Method and device for detecting switching value of pressure switch

ABSTRACT

A method and a device for detecting the switching value of a pressure switch. The device comprises: a pressure generator in communication with a pressure switch by means of pressure piping, a pressure control element, a pressure sensor, and a controller provided with a data processing unit. The pressure sensor is installed on the pressure piping and is electrically connected to the controller. The pressure control element is electrically connected to the pressure generator to control the pressure generator, and is electrically connected to the controller. The pressure sensor transfers the pressure change of the pressure piping to the controller in real time, the data processing unit acquires the value of the pressure change and generates a control instruction according to a preset pressure change rule, and the pressure control element controls the pressure generator to change the pressure within the piping. The device and the method are used to complete the detection of the switching value of a pressure switch, fast detection is achieved, the detection accuracy is improved, the repeatability of the detection result is good, the manual operation cost is reduced and the operation is reliable.

FIELD OF THE INVENTION

The present invention belongs to the pressure detection field, andparticularly relates to a device for detecting the switching value of apressure switch and a detection method utilizing the device.

BACKGROUND OF THE INVENTION

Pressure switches are common pressure control devices. A pressure switchswitches between an ON state and an OFF state to provide an alarm orcontrol signal when the input pressure reaches (rises or drops to) apreset value. The pressure value at which a pressure switch switchesstates is referred to the switching value of the pressure switch,including upper switching value and lower switching value. The pressurevalue of a pressure system can be controlled with a certain range bycontrolling the start, stop or pressurization of the pressure generatorand the opening or closing of the pressure reducing valve in the system.In pressure control processes in industrial domains, the accuracy of thedetection of switching values of pressure switches has direct influenceon pressure control accuracy. Therefore, pressure switches must bechecked and the switching values of the pressure switches must bedetected before the pressure switches can be used.

Common pressure switches are generally categorized into mechanicalpressure switches and electronic pressure switches. In an electronicpressure switch, a pressure sensing element converts the pressure intoan electrical signal, the electrical signal is processed through asignal processing circuit and converted into a digital signal throughA/D conversion, and then the digital signal is processed by a processorto obtain a pressure value; meanwhile, the processor compares thepressure value with a value preset by the user to cause a switchingelement (e.g., mechanical relay or electronic switching element, etc.)to switch on or off. In a mechanical pressure switch, a pressure sensingelement (e.g., a diaphragm, a bellows, or a piston, etc.) converts thepressure into a strain, and then a mechanical mechanism uses the strainto drive a switching element to switch on or off. Usually, a pressureswitch has a pipeline input interface end and an ON-OFF signal outputinterface end, wherein the pipeline input interface end may be connectedto a hydraulic pipeline or pneumatic pipeline to form a path to anexternal pressure pipeline, and the ON-OFF signal output interface endgenerates a digital signal (including ON-OFF signal output type, leveloutput type, and logic signal output type, etc.) to activate a contactof the pressure switch, and is used to connect to a control unit in anindustrial control system to carry out pressure control.

In an existing pressure switch detection system (e.g., as shown in FIG.4), a pressure source 100, a standard pressure gauge 101, and a pressureswitch 103 are connected through an equipressure pipeline 102 to form apath, and a switch state acquisition unit 104 is connected to thepressure switch 103 to detect the open/close of the contact of thepressure switch 103. The pressure source 100 pressurizes ordepressurizes the pressure switch 103 slowly. In this process, thechange of the switch state of the switch is usually detected bylistening to the sound and taking the reading manually, or the ON/OFFstate of the switch may be detected with a multi-meter. In the detectionprocess, the operator has to take the reading in an accurately andtimely manner while evaluating the change of the switch. As a result,some time delay is inevitable in that process. Consequently, a severeerror may exist between the reading and the true value, and amis-reading or mis-evaluation phenomenon may occur easily; the detectionresult may vary each time and the consistency amount multiple readingsmay be poor owing to a non-uniform pressurization/depressurization rateincurred by manual reading and operation; moreover, in such a pressureswitch detection system, the slow pressurization/depressurizationprocess of the pressure switch 103 driven by the pressure source 100 istime-consuming.

CONTENTS OF THE INVENTION

To solve the above-mentioned problems, in one aspect, the presentinvention provides a device for detecting the switching value of apressure switch that achieves high consistency and high accuracy and isconvenient to use.

The above object of the present invention is attained with the followingtechnical solution: A device for detecting the switching value of apressure switch, comprising a pressure generator that communicates withthe pressure switch via a pressure pipeline, a pressure control element,a pressure sensor, and a controller with a data processing unit,wherein, the pressure sensor is installed on the pressure pipeline andelectrically connected to the controller, the pressure control elementis electrically connected to the pressure generator, configured tocontrol the pressure generator, and electrically connected to thecontroller, the data processing unit of the controller is electricallyconnected to the pressure sensor and the pressure switch to acquiredata, analyze and process the acquired data, generate a correspondingcontrol command, and transmit the control command via the pressurecontrol element to the pressure generator.

In the device for detecting the switching value of a pressure switchdescribed above, the controller further comprises a storage unit, whichis electrically connected to and interacts with the pressure controlelement and the pressure sensor, and has an interface for datainteraction with the data processing unit.

The device for detecting the switching value of a pressure switchdescribed above further comprises an electrical interface electricallyconnected to the controller, wherein, the electrical interface is anintegrated component that has different interfaces, including digitalsignal interface, USB interface, serial interface, wireless interface,and Ethernet interface.

The device for detecting the switching value of a pressure switchdescribed above further comprises an external device connected to thecontroller, including computer, liquid crystal display (LCD) or touchscreen.

In another aspect, the present invention provides a method for detectingthe switching value of a pressure switch, which utilizes theabove-mentioned device for detecting the switching value of a pressureswitch to detect the switching value of a pressure switch, and comprisesthe following steps:

Initial value acquisition step: acquiring a pressure value of thepressure switch as an initial upper switching value R₀ and acorresponding pressurization rate as an initial pressurization rate v₁₀at the time of state switching of the pressure switch in apressurization process of the pressure switch via the pressure sensor,or acquiring a pressure value of the pressure switch as an initial lowerswitching value F₀ and a corresponding depressurization rate as aninitial depressurization rate v₂₀ at the time of state switching of thepressure switch in a depressurization process of the pressure switch viathe pressure sensor, by the data processing unit of the controller;

Detected value acquisition step: transmitting a command for adjusting(increasing or decreasing) the pressure in the pressure pipeline to thepressure generator via the pressure control element, acquiring apressure value of the pressure switch as a detected upper switchingvalue R and a corresponding pressurization rate v_(1i) at the time ofstate switching of the pressure switch in a pressurization process ofthe pressure switch via the pressure sensor, or acquiring a pressurevalue as a detected lower switching value F_(i) and a correspondingdepressurization rate v_(2i) at the time of state switching of thepressure switch in a depressurization process of the pressure switch viathe pressure sensor, by the data processing unit, where i=1,2,3 . . . ;

Judgment step: comparing a difference between a maximum value and aminimum value between/among the detected upper switching values(including the initial upper switching value) or the detected lowerswitching values (including the initial lower switching value) that wereacquired in the last two or more times with a specified value δ, by thedata processing unit, and returning to the detected value acquisitionstep if the difference is greater than or equal to the specified valueδ; or taking the detected upper switching value or detected lowerswitching value that was acquired in the last time as the upperswitching value or lower switching value of the pressure switch andoutputting that value, by the data processing unit, if the difference issmaller than the specified value δ.

In the method for detecting the switching value of a pressure switchdescribed above, the controller further comprises a storage unit, whichis electrically connected to and interacts with the pressure controlelement and the pressure sensor, and has an interface for datainteraction with the data processing unit.

In the method for detecting the switching value of a pressure switchdescribed above, the detection device further comprises an electricalinterface electrically connected to the controller, wherein, thepressure switch transmits a switching action signal of the pressureswitch to the controller via the electrical interface.

In the method for detecting the switching value of a pressure switchdescribed above, the detection device further comprises an externaldevice connected to the controller via the electrical interface,wherein, the electrical interface is an integrated component that hasdifferent interfaces, including digital signal interface, USB interface,serial interface, wireless interface and Ethernet interface, and theexternal device may be one or more of computer, liquid crystal display(LCD) and touch screen.

More specifically, the method for detecting the switching value of apressure switch comprises two schemes:

Scheme I

In the existing pressure switch detection system shown in FIG. 4, thepressure source 100 pressurizes or depressurizes the pressure switch 103slowly. In that process, the change of the switch is usually detected bylistening to the sound and evaluated by taking a reading manually, orthe ON/OFF state of the switch may be detected with a multi-meter [VOLTMETER?]. In the detection process, the operator has to take the readingin an accurate and timely manner while detecting the change of theswitch. As a result, some time delay is inevitable in the process.Consequently, a severe error may exist between the reading and the truevalue, and a mis-reading or mis-detection phenomenon may occur easily;the detection result may vary from one time to the next and theconsistency may be poor owing to a non-uniformpressurization/depressurization rate incurred by manual reading andoperation.

In the method for detecting the switching value of a pressure switch asspecified in the existing specification, since the pressure change rateat the time the switching value is detected is not specifiedquantitatively but is only described as “low”, it is very difficult toensure uniformity and accuracy of the detection result; in addition, inthe existing method, usually a rough range of switching value must bespecified.

In “Embodiment 1” in Scheme I, to solve the above problem, a method fordetecting the switching value of a pressure switch is provided whichachieves high accuracy and high consistency and is convenient to use.The method comprises the following steps:

Initial value acquisition step: acquiring a pressure value of thepressure switch as an initial upper switching value R₀ and acorresponding pressurization rate as an initial pressurization rate v₁₀at the time of state switching of the pressure switch in apressurization process of the pressure switch, or acquiring a pressurevalue of the pressure switch as an initial lower switching value F₀ anda corresponding depressurization rate as an initial depressurizationrate v₂₀ at the time of state switching of the pressure switch in adepressurization process of the pressure switch;

Detected value acquisition step: acquiring a pressure value as adetected upper switching value R_(i) and a corresponding pressurizationrate v_(1i) at the time of state switching in a pressurization processof the pressure switch, or acquiring a pressure value as a detectedlower switching value F_(i) and a corresponding depressurization ratev_(2i) at the time of state switching in a depressurization process ofthe pressure switch, in a way that ensures the pressurization rate ordepressurization rate at the time of state switching of the pressureswitch is smaller than the pressurization rate v_(1(i-1)) ordepressurization rate v_(2(i-1)) in the last time of state switching ofthe pressure switch, where i=1,2,3 . . . ;

Judgment step: comparing a difference between a maximum value and aminimum value between/among the detected upper switching values(including the initial upper switching value) or the detected lowerswitching values (including the initial lower switching value) that wereacquired in the last two or more times with a specified value δ, andreturning to the detected value acquisition step if the difference isgreater than or equal to the specified value δ; or taking the detectedupper switching value or detected lower switching value that wasacquired in the last time as the upper switching value or lowerswitching value of the pressure switch, if the difference is smallerthan the specified value δ.

In the detected value acquisition step in the Scheme I, thepressurization rate or depressurization rate is decreased from thepressurization rate v_(1(i-1)) or depressurization rate v_(2(i-1)) inthe last time of state switching of the pressure switch, a rateadjustment value is added to the decreased pressurization rate ordepressurization rate, and then the resultant pressurization rate ordepressurization rate is used to change the pressure in the pipeline viathe pressure control element and the pressure generator; in addition,the rate adjustment value is decreased as the pressure value in thepressure pipeline is closer to the detected upper switching value(including the initial upper switching value) or the detected lowerswitching value (including the initial lower switching value) that wasacquired in the last time; specifically:

In the pressurization process, the rate adjustment value is a functionof the pressure value in the pipeline expressed byΔV_(ij)k(R_(i-1)−p_(j)), and the pressurization rate is expressed byV_(ij)=θv_(1(i-1))+ΔV_(ij), where, ΔV_(ij) is the rate adjustment valuein the detection step j in the detected value acquisition step i, V_(ij)is the pressurization rate in the detected value acquisition step i,v_(1(i-1)) is the pressurization rate when the detected upper switchingvalue was acquired in the detected value acquisition step (i−1) R_(i-1)is the detected upper switching value detected in the detected valueacquisition step (i−1), p_(j) is the pressure value in the pressurepipeline detected in the detection step j, k is a pressure adjustmentfactor, θ is a rate adjustment factor, and k≥0, 0≤θ<1, i=1,2,3, . . . ,j=1,2,3, . . . ; if k=0, the pressurization rate is expressed byV_(i)=θv_(1(i-1)) (see embodiment 1: constant rate pressure controlmethod).

In the depressurization process, the rate adjustment value is a functionof the pressure value in the pipeline expressed byΔV_(ij)=k(p_(j)−F_(i-1)) and the depressurization rate is expressed byV_(ij)=θv_(2(i-1))+ΔV_(ij), where, ΔV_(ij) is the rate adjustment valuein the detection step j in the detected value acquisition step i, V_(ij)is the depressurization rate in the detected value acquisition step i,v_(2(i-1)) is the depressurization rate when the detected lowerswitching value was acquired in the detected value acquisition step(i−1), F_(i-1) is the detected lower switching value detected in thedetected value acquisition step (i−1), p_(j) is the pressure value inthe pressure pipeline detected in the detection step j, k is a pressureadjustment factor, θ is a rate adjustment factor, and k≥0, 0<θ<1,i=1,2,3, . . . , j=1,2,3, . . . ; if k=0, the depressurization rate isexpressed by V_(i)=θv_(2(i-1)) (see embodiment 1: constant rate pressurecontrol method).

The detection method provided in the Embodiment 1 can solve the problemof accuracy and consistency.

In addition, in the prior art pressure switch detection system, as shownin FIG. 3, there is a problem that the pressurization anddepressurization process of the pressure switch 103 driven by thepressure source 100 is slow and time-consuming. Embodiment 2 in Scheme Isolves this problem by providing a method for detecting the switchingvalue of a pressure switch that can accomplish the pressurization and/ordepressurization process quickly.

The difference between the embodiment 2 and the embodiment 1 lies inthat the value of k is k>0 (see embodiment 2: variable rate pressurecontrol method). The detection method provided in the embodiment 2 canrealize quick detection, besides solving the problem of accuracy andrepeatability.

In the Scheme I, the specified value δ in the detected value acquisitionstep is preset accuracy, and its value is within a range of 0.2-0.5times of the accuracy of the pressure switch. The rate adjustment factorθ preferably is θ≥0.3 and θ≤; 0.7.

In the method for detecting the switching value of a pressure switchdescribed above, in the initial value acquisition step, the pressure inthe pressure pipeline is changed at a high pressurization rate ordepressurization rate, till ON-OFF state switching of the pressureswitch is detected; at that point, the pressure value at the time ofstate switching of the pressure switch is acquired as an initial upperswitching value R_(i) or initial lower switching value F_(i), and thepressurization rate or depressurization rate at the time of stateswitching of the pressure switch is taken as an initial pressurizationrate v_(1i) or initial depressurization rate v_(2i).

A device for detecting the switching value of a pressure switchcorresponding to the Scheme I is shown in FIG. 9. The device comprises apressure generator, a pressure sensor, and a pressure pipeline, wherein,the pressure generator and the pressure sensor communicate with thepressure switch through the pressure pipeline, the pressure value in thepressure pipeline is adjusted via the pressure generator, so that thepressure switch is switched between ON state and OFF state; the devicefurther comprises an initial value acquisition unit, a detected valueacquisition unit, and a judgment unit, wherein:

The initial value acquisition unit controls the pressure generator tochange the pressure in the pressure pipeline, acquires a pressure valueas an initial upper switching value R₀ and a correspondingpressurization rate as an initial pressurization rate v₁₀ at the time ofstate switching of the pressure switch in a pressurization process ofthe pressure switch, or acquires a pressure value as an initial lowerswitching value F₀ and a corresponding depressurization rate as aninitial depressurization rate v₂₀ at the time of state switching of thepressure switch in a depressurization process of the pressure switch;

The detected value acquisition unit controls the pressure generator tochange the pressure in the pressure pipeline, acquires a pressure valueas a detected upper switching value R_(i) and a correspondingpressurization rate v_(1i) at the time of state switching of thepressure switch in a pressurization process of the pressure switch oracquires a pressure value as a detected lower switching value F_(i) anda corresponding depressurization rate v_(2i) at the time of stateswitching of the pressure switch in a depressurization process of thepressure switch, in a way that ensures the pressurization rate ordepressurization rate at the time of state switching of the pressureswitch is smaller than the pressurization rate v_(1(i-1)) ordepressurization rate v_(2(i-1)) in the last time of state switching ofthe pressure switch, where i=1,2,3 . . . ;

The judgment unit receives the data values acquired by the detectedvalue acquisition unit, compares the difference between a maximum valueand a minimum value between/among detected upper switching values(including the initial upper switching value) or detected lowerswitching values (including the initial lower switching value) that wereacquired in the last two or more times with a specified value δ, andinstructs the detected value acquisition unit to perform the next timeof acquisition operation if the difference is greater than or equal tothe specified value δ; or takes the detected upper switching value ordetected lower switching value that was acquired in the last time as theupper switching value or lower switching value of the pressure switch,if the difference is smaller than the specified value δ.

Scheme II

To solve the same problem of accuracy and repeatability of the existingpressure switch detection system as shown in FIG. 4 as the embodiment 1in the Scheme I, a “embodiment 3” in the Scheme II provides a method fordetecting the switching value of a pressure switch, which achieves highaccuracy and high repeatability, and is convenient to use. The methodcomprises the following steps:

Initial value acquisition step: acquiring a pressure value of thepressure switch as an initial upper switching value R₀ and acorresponding pressurization rate as an initial pressurization rate v₁₀at the time of state switching of the pressure switch in apressurization process of the pressure switch, or acquiring a pressurevalue of the pressure switch as an initial lower switching value F₀ anda corresponding depressurization rate as an initial depressurizationrate v₂₀ at the time of state switching of the pressure switch in adepressurization process of the pressure switch;

Detected value acquisition step: acquiring a pressure value as adetected upper switching value R_(i) and a corresponding pressurizationrate v_(1i) at the time of state switching of the pressure switch in apressurization process of the pressure switch, or acquiring a pressurevalue as a detected lower switching value F_(i) and a correspondingdepressurization rate v_(2i) at the time of state switching of thepressure switch in a depressurization process of the pressure switch,where i=1,2,3 . . . ;

Estimated value acquisition step: performing fitting estimation for thedetected upper switching values (including the initial upper switchingvalue) or the detected lower switching values (including the initiallower switching value) that were acquired in the last two or more times,and acquires an estimated upper switching value {circumflex over(R)}_(r) or estimated lower switching value {circumflex over (F)}_(r) ofthe pressure switch, where r=1,2,3 . . . ;

Judgment step: comparing the difference between a maximum value and aminimum value between/among the estimated upper switching values or theestimated lower switching values acquired in the last two or more timeswith a specified value δ, and returning to the detected valueacquisition step if the difference is greater than or equal to thespecified value δ; or taking the estimated upper switching value or theestimated lower switching value acquired in the last time as an upperswitching value or lower switching value of the pressure switch, if thedifference is smaller than the specified value δ.

In the detected value acquisition step in the Scheme II, thepressurization rate or depressurization rate is decreased from thepressurization rate v_(1(i-1)) or the depressurization rate v_(2(i-1))in the last time of state switching of the pressure switch, a rateadjustment value is added to the decreased pressurization rate ordepressurization rate, and the resultant pressurization rate ordepressurization rate is used to change the pressure in the pipeline viathe pressure control element and the pressure generator; in addition,the rate adjustment value is decreased as the pressure value in thepressure pipeline is closer to the detected upper switching value(including the initial upper switching value) or the detected lowerswitching value (including the initial lower switching value) that wasacquired in the last time; specifically:

In the pressurization process, the rate adjustment value is a functionof the pressure value in the pipeline expressed byΔV_(ij)k(R_(i-1)−p_(j)), and the pressurization rate is expressed byV_(ij)=θv_(1(i-1))+ΔV_(ij), where, ΔV_(ij) is the rate adjustment valuein the detection step j in the detected value acquisition step i, V_(ij)is the pressurization rate in the detected value acquisition step i,v_(1(i-1)) is the pressurization rate when the detected upper switchingvalue was acquired in the detected value acquisition step (i−1), R_(i-1)is the detected upper switching value detected in the detected valueacquisition step (i−1), p_(j) is the pressure value in the pressurepipeline detected in the detection step i, k is a pressure adjustmentfactor, θ is a rate adjustment factor, and k≥0, 0<θ<1 i=1,2,3, . . .j=1,2,3, . . . ; if k=0, the pressurization rate is expressed byV_(i)=θv_(1(i-1)) (see embodiment 3: constant rate pressure controlmethod based on polynomial fitting).

In the depressurization process, the rate adjustment value is a functionof the pressure value in the pipeline expressed byΔV_(ij)=k(p_(j)−F_(i-1)), and the depressurization rate is expressed byV_(ij)=θv_(2(i-1))+ΔV_(ij), where, ΔV_(ij) is the rate adjustment valuein the detection step j in the detected value acquisition step i, V_(ij)is the depressurization rate in the detected value acquisition step i,v_(2(i-1)) is the depressurization rate when the detected lowerswitching value was acquired in the detected value acquisition step(i−1), F_(i-1) is the detected lower switching value detected in thedetected value acquisition step (i−1), p_(j) is the pressure value inthe pressure pipeline detected in the detection step j, k is a pressureadjustment factor, θ is a rate adjustment factor, and k≥0, 0<θ<1,=1,2,3, . . . j=1,2,3, . . . ; if k=0, the depressurization rate isexpressed by V_(i)=θv_(2(i-1)) (see embodiment 3: constant rate pressurecontrol method based on polynomial fitting).

The detection method provided in the embodiment 3 can solve the problemof accuracy and repeatability.

To solve the same time-consuming problem in the pressure switchdetection system as shown in FIG. 4 as the embodiment 2 in the Scheme I,an “embodiment 4” in the Scheme II provides a method for detecting theswitching value of a pressure switch, which can accomplish thepressurization and/or depressurization process quickly.

The difference between the embodiment 4 and the embodiment 3 lies inthat the value of k is k>0 (see embodiment 4: variable rate pressurecontrol method based on polynomial fitting). The detection methodprovided in the embodiment 4 can realize quick detection, besidessolving the problem of accuracy and repeatability.

In the Scheme II, in the estimated value acquisition step, fittingestimation is performed for the relation between detected upperswitching value and pressurization rate or between detected lowerswitching value and depressurization rate with a polynomial fittingmethod based on least square, and a corresponding estimated switchingvalue when the pressurization rate or depressurization rate is zero istaken as an estimated upper switching value or estimated lower switchingvalue.

In the judgment step, the specified value δ is preset accuracy, and itsvalue is within a range of 0.2-0.5 times of the accuracy of the pressureswitch.

In the initial value acquisition step, the pressure in the pressurepipeline is changed at a high pressurization rate or depressurizationrate, till ON-OFF state switching of the pressure switch is detected; atthat point, the pressure value at the time of state switching of thepressure switch is acquired as an initial upper switching value R_(i) orinitial lower switching value F_(i) and the pressurization rate ordepressurization rate at the time of state switching of the pressureswitch is taken as an initial pressurization rate v_(1i) or initialdepressurization rate v_(2i).

A device for detecting the switching value of a pressure switchcorresponding to the Scheme II is shown in FIG. 10. The device comprisesa pressure generator, a pressure sensor, and a pressure pipeline,wherein, the pressure generator and the pressure sensor communicate withthe pressure switch through the pressure pipeline, the pressure value inthe pressure pipeline is adjusted via the pressure generator, so thatthe pressure switch is switched between ON state and OFF state; wherein,the device further comprises an initial value acquisition unit, adetected value acquisition unit, an estimated value acquiring unit, anda judgment unit, wherein:

The initial value acquisition unit controls the pressure generator tochange the pressure in the pressure pipeline, acquires a pressure valueas an initial upper switching value R₀ and a correspondingpressurization rate as an initial pressurization rate v₁₀ at the time ofstate switching of the pressure switch in a pressurization process ofthe pressure switch, or acquires a pressure value as an initial lowerswitching value F₀ and a corresponding depressurization rate as aninitial depressurization rate v₂₀ at the time of state switching of thepressure switch in a depressurization process of the pressure switch;

The detected value acquisition unit controls the pressure generator tochange the pressure in the pressure pipeline, acquires a pressure valueas a detected upper switching value R_(i) and a correspondingpressurization rate v_(1i) at the time of state switching of thepressure switch in a pressurization process of the pressure switch, oracquires a pressure value as a detected lower switching value F_(i) anda corresponding depressurization rate v_(2i) at the time of stateswitching of the pressure switch in a depressurization process, wherei=1,2,3 . . . ;

The estimated value acquiring unit receives the data values acquired bythe detected value acquisition unit, performs fitting estimation for thedetected upper switching values (including the initial upper switchingvalue) or the detected lower switching values (including the initiallower switching value) that were acquired in the last two or more times,and acquires an estimated upper switching value {circumflex over(R)}_(r) or estimated lower switching value {circumflex over (F)}_(r) ofthe pressure switch, where r=1,2,3 . . . ;

The judgment unit receives the data values acquired by the estimatedvalue acquisition unit, compares the difference between a maximum valueand a minimum value between/among estimated upper switching values orthe estimated lower switching values that were acquired in the last twoor more times with a specified value δ, and instructs the detected valueacquisition unit to perform the next time of acquisition operation ifthe difference is greater than or equal to the specified value δ; ortakes the estimated upper switching value or the estimated lowerswitching value acquired in the last time as an upper switching value orlower switching value of the pressure switch, if the difference issmaller than the specified value δ.

With the technical scheme described above, the present invention attainsthe following technical effects: In the present invention, the pressurechange in a pressure pipeline is transmitted via the pressure sensor tothe controller, the data processing unit installed in the controlleracquires the pressure change, generates a control command under presetpressure change rules, and controls the pressure generator via thepressure control element to change the pressure in the pipeline; thedetection of the switching value of the pressure switch is accomplishedwith a cyclic detection approach. The device provided in the presentinvention can accomplish the detection of the switching value of apressure switch, intelligently and quickly, with improved accuracy andconsistency, with reduced labor cost, simplified the operation andreliability.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of the structure of the device for detectingthe switching value of a pressure switch provided in an embodiment ofthe present invention;

FIG. 2 is a flow chart of the method for detecting the switching valueof a pressure switch in the Scheme I in the present invention;

FIG. 3 is a flow chart of the method for detecting the switching valueof a pressure switch in Scheme II in the present invention;

FIG. 4 is a schematic diagram of an existing pressure switch detectionsystem;

FIG. 5 is a diagram illustrating the relation between the pressurechange rate and the detected pressure switching value in embodiment 1and embodiment 2;

FIG. 6 is a diagram illustrating the relation between the pressurechange rate and the detected pressure switching value in embodiment 3;

FIG. 7 is a diagram illustrating the relation between the pressurechange rate and the detected pressure switching value in embodiment 4;

FIG. 8 is a diagram illustrating the relation between the pressurechange rate and the detected pressure switching value in embodiment 5;

FIG. 9 is a block diagram of the structure of the device for detectingthe switching value of a pressure switch corresponding to the Scheme Iin the present invention; and

FIG. 10 is a block diagram of the structure of the device for detectingthe switching value of a pressure switch corresponding to the Scheme Iin the present invention.

In the figures:

1—pressure generator; 2—pressure control element; 3—pressure pipeline;4—pressure sensor; 5—controller; 51—storage unit; 52—data processingunit; 6—electrical interface; 7—pipeline interface; 8—pressure switch;

100—pressure source; 101—standard pressure gauge; 102—equipressurepipeline; 103—pressure switch; 104—switch state acquisition unit

DETAILED DESCRIPTION OF THE EMBODIMENTS

Hereunder the method and device for detecting the switching value of apressure switch provided in the present invention will be described inspecific embodiments, with reference to the accompanying drawings.

The present invention is applicable to detection of the switching valueof various pressure switches. Though the present invention is describedin the embodiments with reference to an electronic pressure switch, thepresent invention is not limited to those specific exemplaryembodiments; rather, the present invention is intended to encompass allequivalent and alternative forms within the range of the presentinvention. All other embodiments obtained by those having ordinaryskills in the art on the basis of the embodiments described in thepresent invention without expending any creative labor shall be deemedas falling in the scope of disclosure in the present invention.

FIG. 1 is a block diagram of the structure of the device for detectingthe switching value of a pressure switch provided in an embodiment ofthe present invention. As shown in FIG. 1, the device comprises apressure generator 1, a pressure control element 2, a pressure pipeline3, a pressure sensor 4, and a controller 5, wherein, the pressuregenerator 1 and the pressure sensor 4 are connected through the pressurepipeline 3 to form a physical path (as indicated by the bold line inFIG. 1), and an external pressure switch 8 that communicates physicallywith the path via a pipeline interface 7; the pressure control element 2is connected to the pressure generator 1 and is configured to controlthe pressure generator 1, pressure control element 2 is connected to thecontroller 5 to store pressure control data in the controller 5,receives control commands from the controller 5 and transmits thecontrol commands to the pressure generator 1; the controller 5 iselectrically connected to the pressure sensor 4 and logically connectedto the external pressure switch 8 via the electrical interface 6(including electrical connection or wireless connection, etc.) toreceive signals from the pressure sensor 4 and the pressure switch 8,analyze and process the received data, and transmit generated controlcommands to the pressure generator 1 via the pressure control element 2;the pressure pipeline 3 is connected to a pipeline input interface endof the pressure switch 8 via the pipeline interface 7 and transmits thepressure generated by the pressure generator 1 to the pressure switch 8;additionally, the controller 5 is logically connected to an ON-OFFsignal output end of the pressure switch 8 to receive contact actionsignals from the pressure switch 8.

Wherein the pressure generator 1 may be a pneumatic pressure generatoror hydraulic pressure generator, and is driven by a pressure pump; thepressure generator 1 receives control commands from the controller 5 viathe pressure control element 2 to control the pressure pump topressurize or depressurize at different rates; in addition, the pressurecontrol element 2 can transmit the state of the pressure generator 1 tothe controller 5 and to an external device 9 (e.g., a computer, an LCD,or a touch screen) for display.

The pressure control element 2 may be a separate element disposedbetween the pressure generator 1 and the controller 5, serving as anintermediary for signal transmission and conversion; for example, thepressure control element 2 may be an existing integrated controlelement; alternatively, it may be integrated in the controller 5 or thepressure generator 1 to control the pressure pump to pressurize ordepressurize at different rates. The pressure control element 2 canaccept control commands from the controller 5 and transmit the state ofthe pressure generator 1 to the controller 5 and then transmit the stateof the pressure generator 1 via the controller 5 to the external device9.

The pressure sensor 4 is installed on the pressure pipeline 3 andconfigured to detect the pressure in the pressure pipeline 3 and convertthe pressure signal to an electrical signal and transmit the electricalsignal to the controller 5.

The electrical interface 6 is an integrated component that has one ormore electrical signal interfaces, and can support input and output ofdifferent electrical signals, wherein, the electrical interface mayinclude a digital signal interface, a USB interface, a serial interface,and an Ethernet interface, etc. The electrical interface 6 can beelectrically connected to the ON-OFF signal output end of the pressureswitch 8 to receive electrical signals of contact actions of thepressure switch 8 and transmit the electrical signals to the controller5, or can be electrically connected to the external device 9 (e.g., acomputer, an LCD, or a touch screen, etc.), so that the controller 5 andthe external device 9 can perform data interaction with each other viathe electrical interface for data acquisition, result display, programdownloading, parameter setting, remote debugging, and system updating,etc. Therefore, the device in the present invention may be equipped witha display screen via the electrical interface 6 and configured into ahandheld device that can be used in the field conveniently;alternatively, the device may be used as a stationary device andconnected to a computer system for remote monitoring.

The pipeline interface 7 may be a fixed interface arranged on thepressure pipeline 3 or a removable and replaceable interface that can bereplaced according to the shape of the pipeline input interface end ofthe pressure switch 8.

The controller 5 may comprise a storage unit 51 and a data processingunit 52, wherein, the storage unit 51 is electrically connected to thepressure control element 2 and the pressure sensor 4, and electricallyconnected to the pressure switch 8 via the electrical interface 6 toreceive, transmit and store data, and has an interface for datainteraction with the data processing unit 52; the data processing unit52 receives data from the storage unit 51, analyzes and process thedata, and transmits generated control commands to the pressure controlelement 2 via the storage unit 51.

The data processing unit 52 of the controller 5 sends control commandsto the pressure generator 1 via the storage unit 51 to cause thepressure generator 1 to change the pressure in the pressure pipeline 3and receives a pressure value acquired by the pressure sensor 4 andstate information of the pressure switch 8 so as to accomplish dataprocessing in the detection of the switching value of the pressureswitch.

Most existing detection methods for detecting the switching value of apressure switch are implemented on the basis of the following mechanism:The pressure value that triggers a state change of the switch in apressurization process is referred to as an upper switching value R₀(true value), the pressure value that triggers a state change of theswitch in a depressurization process is referred to as a lower switchingvalue F (true value), and R>F; then, R−F is referred to as a returndifference. Owing to the existence of the return difference, theoperating stability of the pressure switch is improved. The magnitude ofthe return difference may vary, depending on the specific requirement inthe application scenario. In the measurement process, the pressure valuemeasured by the pressure sensor 4 is an detected upper switching valueor detected lower switching value, denoted as R_(i) or F_(i) and themeasurement error ε_(i) is the value obtained by subtracting the truevalue from the detected switching value in the time i, i.e.,ε_(1i)=R_(i)−R, ε_(2i)=F_(i)−F, where, i is the sequence number ofmeasurement, R is the true upper switching value, R_(i) is the upperswitching value detected in the time i, and ε_(1i) is the detectionerror of the upper switching value in the time i; F is the true lowerswitching value, F_(i) is the lower switching value detected in the timei, and ε_(2i) is the detection error of the lower switching value in thetime i.

When the pressure in the pressure pipeline 3 reaches a switching point,a contact actuating signal has to be acquired through several links,including pressure measurement and comparison of the pressure switch,switch driving, switch measurement and time for response to switchingcapturing, and time for reading pressure sensor, etc. Owing to thosefactors, the detected switching value may be greater than or smallerthan the true switching value.

Therefore, in the measuring process, the time delay mainly consists oftwo parts: one part is the delay time t₁ from the time the pressurevalue reaches the switching point to the time a switching value ofcontact action is outputted, and the other part is the delay time t₂from the time the switching value is received to the time the reading ofthe pressure sensor is received. Owing to the joint influence in the twoaspects, ε_(1i)=ε₁₁+ε₁₂, and ε_(2i)=ε₂₁+ε₂₂, where, ε_(1i) is thedetection error of upper switching value, ε₁₁ is the error incurred bythe delay time t₁, and ε₁₂ is the error incurred by the delay time t₂;ε_(2i) is the detection error of lower switching value, ε₂₁ is the errorincurred by the delay time t₁, and ε₂₂ is the error incurred by thedelay time t₂. Usually, t₁ and t₂ are relatively small, and the averagepressure change rate v in the time period may be regarded as a fixedvalue, i.e., ε_(1i)=ε₁₁+ε₁₂=v(t₁+t₂), and ε_(2i)=ε₂₁+ε₂₂=v(t₁+t₂); inseveral detection processes, the delays of the pressure sensor and thepressure switch remain unchanged essentially; therefore, the detectionerror ε_(1i) of upper switching value or the detection error ε_(2i) oflower switching value is essentially proportional to the pressure changerate at the time the pressure switch is triggered to act.

If the amplitude of pressure change is Δp, the measurement time is t,the pressure change rate is v constantly, then t=Δp/v if the measurementtime t is enough, i.e., the measurement time t is approximatelyinversely proportional to the pressure change rate v.

On that basis, on one hand, to detect an accurate switching value of thepressure switch, it is desirable that the pressure change rate v isclose to zero at the time of ON-OFF state switching of the pressureswitch; on the other hand, to save measurement time, it is desirablethat the pressure scanning can be executed at a high pressure changerate v. In actual practice, the detection result of the switching pointof the pressure switch may be inaccurate because the pressure changerate is too high; the repeatability is poor because the pressure changerates in the detection processes are inconsistent.

It can be seen from the above analysis: the lower the rate of pressurechange at the time of state switching of the pressure switch 8, thehigher the detection accuracy of the switching value of the pressureswitch. Therefore, when the switching value of the pressure switch isdetected with the method provided in the present invention, in which thepressure change rate gradually approaches zero, the detected value willapproach the true value; in addition, utilizing the specified value δfor preset accuracy as a evaluation criterion for terminating thedetection loop, the above-mentioned object can be attained.

Hereunder the method for detecting the switching value of a pressureswitch with the device provided in the present invention will be furtherdetailed. Two implementation schemes are put forward in the presentinvention.

Scheme I

FIG. 2 is a flow chart of the method for detecting the switching valueof a pressure switch in the Scheme I. The method can be implemented withthe device for detecting the switching value of a pressure switch shownin FIG. 1 or 9. The method for detecting the switching value of apressure switch comprises the following steps:

S100. Initial value acquisition step: acquiring a pressure value as aninitial upper switching value R₀ and a corresponding pressurization rateas an initial pressurization rate v₁₀ at the time of state switching ofthe pressure switch 8 in a pressurization process of the pressure switch8, or acquiring a pressure value as an initial lower switching value F₀and a corresponding depressurization rate as an initial depressurizationrate v₂₀ at the time of state switching of the pressure switch 8 in adepressurization process of the pressure switch 8.

In that step, the pressure in the pressure pipeline 3 is changed at ahigh pressurization rate or depressurization rate, till ON-OFF stateswitching of the pressure switch 8 is detected; at that point, thepressure value at the time of state switching of the pressure switch 8is acquired with the pressure sensor and taken as an initial upperswitching value R₀ or initial lower switching value F₀ and thepressurization rate or depressurization rate at the time of stateswitching of the pressure switch 8 is taken as an initial pressurizationrate v₁₀ or initial depressurization rate v₂₀.

Here, in the initial value acquisition process, the initialpressurization rate or initial depressurization rate is usuallydetermined from an empirical value according to the performance of thepressure switch 8; usually, the initial pressurization rate or initialdepressurization rate is selected near the upper limit of the empiricalvalue of pressurization rate or empirical value of depressurizationrate, so as to approximate to the switching value of the pressure switch8 as soon as possible and thereby reduce the detection time.

The pressurization rate or depressurization rate at the time of stateswitching of the pressure switch can be obtained by computing with aprogram; namely, the process from the time the pressure sensor 4 readsthe pressure value in the pressure pipeline 3 to the next time thepressure sensor 4 reads the pressure value in the pressure pipeline 3 isused as a detection step, and the pressurization rate v₁₀ ordepressurization rate v₂₀ at the time of state switching of the pressureswitch is determined by subtracting the pressure value detected in theprevious detection step from the pressure value detected at the time ofstate switching of the pressure switch and then dividing the result bythe time used in the detection step; alternatively, if the pressuresensor 4 has a rate measurement function, the pressurization rate v₁₀ ordepressurization rate v₂₀ at the time of state switching of the pressureswitch may be recorded by the pressure sensor 4; or the pressurizationrate or depressurization rate at the time of state switching of thepressure switch 8 may be set on the basis of an empirical value.

S200. Detected value acquisition step: acquiring a pressure value as adetected upper switching value v_(1(i-1)) and a correspondingpressurization rate v_(2(i-1)) at the time of state switching in apressurization process of the pressure switch, or acquiring a pressurevalue as a detected lower switching value R_(i) and a correspondingdepressurization rate v_(1i) at the time of state switching in adepressurization process of the pressure switch, in a way that ensuresthe pressurization rate or depressurization rate at the time of stateswitching of the pressure switch is smaller than the pressurization rateF_(i) or depressurization rate v_(2i) in the last time of stateswitching of the pressure switch, where i=1,2,3 . . . ;

In the above detected value acquisition step, in the process from thetime the pressure value is detected initially to the time of stateswitching of the pressure switch 8, the pressurization rate ordepressurization rate may be any value within a reasonable range for thepressure switch; preferably, the pressure in the pressure pipeline 3 ischanged at a high pressurization rate or depressurization rate, whichmay be an approximately constant pressurization rate or depressurizationrate or a varying pressurization rate or depressurization rate; forexample, the pressurization rate or depressurization rate in thedetected value acquisition step may be a function of the detectedpressure value in the pressure pipeline 3; at the time of stateswitching of the pressure switch 8, a criterion that the pressurizationrate or depressurization rate is smaller than the pressurization ratev_(1(i-1)) or depressurization rate v_(2(i-1)) in the last time of stateswitching of the pressure switch 8 is met.

S300. Judgment step: comparing a difference between a maximum value anda minimum value between/among the detected upper switching values(including the initial upper switching value) or the detected lowerswitching values (including the initial lower switching value) that wereacquired in the last two or more times with a specified value δ, andreturning to the detected value acquisition step if the difference isgreater than or equal to the specified value δ; or taking the detectedupper switching value or detected lower switching value that wasacquired in the last time as the upper switching value or lowerswitching value of the pressure switch, if the difference is smallerthan the specified value δ.

In the judgment step of the method, the difference between detectedswitching values acquired in the last two times may be compared with thespecified value δ to judge whether the method should be terminated, orthe difference between a maximum value and a minimum value among thedetected switching values acquired in the last three or more times maybe compared with the specified value δ to judge whether the methodshould be terminated, wherein, the specified value δ may be setaccording to the accuracy of the pressure switch 8 and the requirementfor accuracy in the application scenario, and the specified value δ maybe a fixed value or a non-fixed value; for example, the specified valuesδ used in the judgment steps in two detection processes may be differentfrom each other; the switching value of the pressure switch obtainedwith the latter method has higher reliability, and accordingly thedetection time may be longer. A trade-off may be made according to thedetection requirement.

Optionally, the method may further comprise an initialization stepbefore the step S100 to set the parameters involved in the method; forexample, the specified value δ may be set; other parameters to be setmay be determined according to the specific embodiment; that step may beneglected if the parameter values are fixed to default values.

Optionally, the method may further comprise an output step after thejudgment step S300, i.e., recording the detected upper switching valueand detected lower switching value obtained in the last cycle as upperswitching value and lower switching value of the pressure switch 8 inthe controller 5, and transmitting the result to the external device 9.

Different variants of the implementation process of the above-mentionedsteps may be possible, according to different embodiments.

The method may be used to detect the upper switching value or lowerswitching value of a pressure switch separately, and may also be used todetect the upper switching value and lower switching value of a pressureswitch at the same time.

Hereunder two different embodiments (embodiment 1 and embodiment 2) willbe introduced in detail, in an example in which the upper switchingvalue and lower switching value of a pressure switch are detected at thesame time and the difference between a maximum value and a minimum valuebetween the detected switching values acquired in the last two times iscompared with the specified value δ.

Embodiment 1: Constant Rate Pressure Control Method

Please see the flow chart in FIG. 2. In the embodiment 1, the switchingvalue of a pressure switch is detected through the following process:

Initial value acquisition step: the pressure generator 1 changes thepressure in the pressure pipeline 3 at a high pressurization rate ordepressurization rate, till ON-OFF state switching of the pressureswitch 8 is detected; at that point, the pressure sensor 4 acquires thepressure value in the pressure pipeline 3 as an initial upper switchingvalue R₀ or initial lower switching value F₀ and the correspondinginitial pressurization rate v₁₀ or initial depressurization rate v₂₀ atthe time of state switching of the pressure switch 8, and the acquiredvalues are stored in the controller 5.

Detected value acquisition step: the pressure generator 1 increases thepressure in the pressure pipeline 3 from the lower switching valueF_((i-1)) at a pressurization rate V_(i)=θV_(1(i-1)), the upperswitching value acquired by the pressure sensor 4 at the time of stateswitching of the pressure switch 8 is taken as a detected upperswitching value R_(i), and the pressurization rate v_(1i) at the time ofstate switching of the pressure switch 8 is acquired; the pressuregenerator 1 decreases the pressure in the pressure pipeline 3 from theupper switching value R_(i) at a depressurization rateV_(i)=θV_(2(i-1)), the lower switching value acquired by the pressuresensor 4 at the time of state switching of the pressure switch 8 istaken as a detected lower switching value F_(i), the pressurization ratev_(2i) at the time of state switching of the pressure switch 8 isacquired, and the acquired values are stored in the controller 5, where,i is the cycle index, θ is the rate adjustment factor, and i=1,2,3 . . ., 0<θ<1.

Judgment step: If r≥1 and the following criterion is met:

max(R_(i-1), R_(i))−min(R_(i-1), R_(i))<δ and max(F_(i-1),F_(i))−min(F_(i-1), F_(i))<δ, then the detection is terminated, thedetected upper switching value and detected lower switching valueobtained in the last cycle are taken as upper switching value and lowerswitching value of the pressure switch 8 and stored in the controller 5,and the loop is exited; otherwise the cycle index i is incremented by 1,and the process turns to the detected value acquisition step, wherein,the specified value δ is preset accuracy, and its value is 0.2-0.5 timesof the accuracy of the pressure switch 8.

In the above process, if the parameters (e.g., specified value δ and therate adjustment factor θ) are to be set again, the embodiment mayfurther comprise an initialization step; if the device is connected toan external device 9, the embodiment 1 may further comprise an outputstep.

In the above process, the number of cycles depends on the presetspecified value δ, rate adjustment factor θ, and initial pressurizationrate v₁₀ and/or initial depressurization rate v₂₀, etc.; in the detectedvalue acquisition step of the method, the higher the rate adjustmentfactor θ is, the less the pressurization rate or depressurization rateis decreased in each time of detection, and thereby the shorter therequired time is; however, in such a case, usually the times ofdetection required to reach required accuracy will be increased, and thetotal detection time will be longer accordingly; in contrast, the lowerthe rate adjustment factor θ is, the more the pressurization rate ordepressurization rate is decreased in each time of detection;accordingly, usually the times of detection will be reduced, but theexecution time in each time of detection will be longer. In addition, ifthe change of pressurization rate or depressurization rate in each timeof detection from the pressurization rate or depressurization rate inthe last time of state switching of the pressure switch is very small,the change of the obtained detected upper switching value or detectedlower switching value of the pressure switch will be very small;especially, in a case that the pressurization rate or depressurizationrate is great in itself, the difference between the obtained upperswitching value or lower switching value of the pressure switch and thetrue value may be great, though the difference between the detectedupper switching values or detected lower switching values obtained intwo times meets the judgment criterion in the judgment step. Througharduous study, the inventor has found: for the constant rate pressurecontrol method, the above defect can be eliminated by controlling therange of the rate adjustment factor θ to be 0.3≤θ≤0 0.7. Usually thespecified value δ is set with reference to the nominal value of thepressure switch and the requirement for accuracy in the applicationscenario, and the value range may be 0.2-0.5 times of the accuracy ofthe pressure switch 8; the value range of the specified value δ being0.2-0.5 times of the accuracy of the pressure switch 8 means that thespecified value δ may be a fixed value or non-fixed value within a rangeof 0.2-0.5 times of the accuracy of the pressure switch 8; for example,the specified values δ used in the judgment steps in two detectionprocesses may be different from each other.

Embodiment 2: Variable Rate Pressure Control Method

In order to further reduce the detection time while meeting thespecified value δ that is used as preset accuracy, the above-mentionedembodiment 1 of the method is improved by using real-time varyingpressurization rate and depressurization rate in each time of detection,i.e., the pressure change rate is higher when the pressure is fartherfrom the state switching point of the pressure switch, so as to savetime; the pressure change rate is lower when the pressure is closer tothe state switching point of the pressure switch, to reduce thedetection error. In the detection process, the process from the time thepressure sensor 4 reads the pressure value in the pressure pipeline 3 tothe next time the pressure sensor 4 reads the pressure value in thepressure pipeline 3 is used as a detection step; the process throughwhich the detection of an upper switching value and an lower switchingvalue of the pressure switch is accomplished is used as a cycle.

The steps included in the variable rate pressure control method in theembodiment 2 are essentially the same as the steps in the embodiment 1,except the rules under which the pressure generator 1 changes thepressure in the pressure pipeline 3 in the detected value acquisitionstep. The detected value acquisition step in the embodiment 2 is asfollows:

Detected value acquisition step: the pressure generator 1 increases thepressure in the pressure pipeline 3 from the lower switching valueF_(i-1) at a pressurization rate V_(ij)=θv_(1(i-1))+k(R_(i-1)−p_(j)),the upper switching value acquired by the pressure sensor 4 at the timeof state switching of the pressure switch 8 is taken as a detected upperswitching value R_(i), and the pressurization rate v_(1i) at the time ofstate switching of the pressure switch 8 is acquired, where, i is thecycle index, i=1,2,3, . . . , j is the detection step index, j=1,2,3, .. . , k is the pressure adjustment factor, θ is the rate adjustmentfactor, 0<k, and 0<θ<1; p_(j) is the pressure value detected by thepressure sensor unit 3 in the detection step j; v_(1(i-1)) is thepressurization rate or initial pressurization rate at the time thedetected upper switching value is acquired in the detected valueacquisition step (i−1), and R_(i-1) is the detected upper switchingvalue or initial upper switching value detected in the detected valueacquisition step i−1;

the pressure generator 1 decreases the pressure in the pressure pipeline3 from the detected upper switching value R_(i) at a depressurizationrate V_(ij)=θv_(2(i-1))+k(p_(j)−F_(i-1)) the lower switching valueacquired by the pressure sensor 4 at the time of state switching of thepressure switch 8 is taken as a detected lower switching value F_(i),and the pressurization rate v_(2i) at the state switching of thepressure switch 8 is acquired; and the acquired values are stored in thecontroller 5; where, p_(j) is the pressure value detected by thepressure sensor unit 3 in the detection step j; v_(2(i-1)) is thedepressurization rate or initial depressurization rate at the time ofstate switching of the pressure switch 8 in the detected valueacquisition step (i−1), and F_(i-1) is the detected lower switchingvalue or initial lower switching value detected in the detected valueacquisition step i−1.

Likewise, this embodiment may further comprise an initialization stepand/or an output step.

The pressure in the pressure pipeline 3 is changed at a real-timevarying pressurization rate or depressurization rate, the detected upperswitching value or detected lower switching value of the pressure switchis detected, and the pressure adjustment factor k is a fixed valuegreater than zero. Likewise, the defect related with the range of therate adjustment factor θ as described in the embodiment 1 must beeliminated too. For the variable rate pressure control method, the rangeof the rate adjustment factor θ is controlled to be 0.3≤θ≤0.7. Usuallythe specified value δ is set with reference to the nominal value of thepressure switch and the requirement for accuracy in the applicationscenario, and the value range may be 0.2-0.5 times of the accuracy ofthe pressure switch 8; the value range of the specified value δ being0.2-0.5 times of the accuracy of the pressure switch 8 means that thespecified value δ may be a fixed value or non-fixed value within a rangeof 0.2-0.5 times of the accuracy of the pressure switch 8; for example,the specified values δ used in the judgment steps in two detectionprocesses may be different from each other.

The method can further reduce the detection time so that the detectedupper switching value or detected lower switching value approaches thetrue value quickly and achieves high consistency.

Scheme II

FIG. 3 is a flow chart of the method for detecting the switching valueof a pressure switch in the Scheme II. The method can be implementedwith the device for detecting the switching value of a pressure switchshown in FIG. 1 or 10. The method for detecting the switching value of apressure switch comprises the following steps:

S10. Initial value acquisition step: acquiring a pressure value as aninitial upper switching value R₀ and a corresponding pressurization rateas an initial pressurization rate v₁₀ at the time of state switching ofthe pressure switch 8 in a pressurization process of the pressure switch8, or acquiring a pressure value as an initial lower switching value F₀and a corresponding depressurization rate as an initial depressurizationrate v₂₀ at the time of state switching of the pressure switch 8 in adepressurization process of the pressure switch 8.

In that step, the pressure in the pressure pipeline 3 is changed at ahigh pressurization rate or depressurization rate, till ON-OFF stateswitching of the pressure switch 8 is detected; at that point, thepressure value at the time of state switching of the pressure switch 8is acquired with the pressure sensor and taken as an initial upperswitching value R₀ or initial lower switching value F₀, and thepressurization rate or depressurization rate at the time of stateswitching of the pressure switch 8 is taken as an initial pressurizationrate v₁₀ or initial depressurization rate v₂₀.

Here, in the initial value acquisition process, the initialpressurization rate or initial depressurization rate is usuallydetermined from an empirical value according to the performance of thepressure switch 8; usually, the initial pressurization rate or initialdepressurization rate is selected near the upper limit of the empiricalvalue of pressurization rate or empirical value of depressurizationrate, so as to approximate to the switching value of the pressure switch8 as soon as possible and thereby reduce the detection time.

The pressurization rate or depressurization rate at the time of stateswitching of the pressure switch can be obtained by computing with aprogram; namely, the process from the time the pressure sensor 4 readsthe pressure value in the pressure pipeline 3 to the next time thepressure sensor 4 reads the pressure value in the pressure pipeline 3 isused as a detection step, and the pressurization rate v₁₀ ordepressurization rate v₂₀ at the time of state switching of the pressureswitch is determined by subtracting the pressure value detected in theprevious detection step from the pressure value detected at the time ofstate switching of the pressure switch and then dividing the result bythe time used in the detection step; alternatively, if the pressuresensor 4 has a rate measurement function, the pressurization rate v₁₀ ordepressurization rate v₂₀ at the time of state switching of the pressureswitch may be recorded by the pressure sensor 4; or the pressurizationrate or depressurization rate at the time of state switching of thepressure switch 8 may be set on the basis of an empirical value.

S20. Detected value acquisition step: acquiring a pressure value as adetected upper switching value R_(i) and a corresponding pressurizationrate v_(1i) at the time of state switching of the pressure switch 8 in apressurization process of the pressure switch 8, or acquiring a pressurevalue as a detected lower switching value F_(i) and a correspondingdepressurization rate v_(2i) at the time of state switching of thepressure switch 8 in a depressurization process of the pressure switch8, where i=1,2,3 . . . ;

In the above detected value acquisition step, in the process from thetime the detection is commenced to the time of state switching of thepressure switch 8, the pressurization rate or depressurization rate maybe any value within a reasonable range; preferably, the pressure in thepressure pipeline 3 is changed at a high pressurization rate ordepressurization rate, which may be an approximately constantpressurization rate or depressurization rate or a varying pressurizationrate or depressurization rate; for example, the pressurization rate ordepressurization rate in the detected value acquisition step is afunction of the detected pressure value in the pressure pipeline 3.

S30. Estimated value acquisition step: performing fitting estimation forthe detected upper switching values (including the initial upperswitching value) or the detected lower switching values (including theinitial lower switching value) that were acquired in the last two ormore times, and acquires an estimated upper switching value {circumflexover (R)}_(r) or estimated lower switching value {circumflex over(F)}_(r) of the pressure switch, where r=1,2,3 . . . .

In the estimated value acquisition step S30, fitting estimation may beperformed with a polynomial fitting method based on least square,because, for a low order equation, the least square method utilizes anoptimal square approximation scheme to approximate a function uniformly,and is simple and easy to use, and highly practical.

S40. Judgment step: comparing the difference between a maximum value anda minimum value between/among the estimated upper switching values orthe estimated lower switching values acquired in the last two or moretimes with a specified value δ, and returning to the detected valueacquisition step S20 if the difference is greater than or equal to thespecified value δ; or taking the estimated upper switching value or theestimated lower switching value acquired in the last time as an upperswitching value or lower switching value of the pressure switch, if thedifference is smaller than the specified value δ.

In the judgment step S40 of the method, the difference between estimatedswitching values acquired in the last two times may be compared with thespecified value δ to judge whether the method should be terminated, orthe difference between a maximum value and a minimum value among theestimated switching values acquired in the last three or more times maybe compared with the specified value δ to judge whether the methodshould be terminated, wherein, the specified value δ may be setaccording to the accuracy of the pressure switch 8 and the requirementfor accuracy in the application scenario, and the specified value δ maybe a fixed value or a non-fixed value; for example, the specified valuesδ used in the judgment steps in two detection processes may be differentfrom each other; the switching value of the pressure switch obtainedwith the latter method has higher reliability, and accordingly thedetection time may be longer. A trade-off may be made according to thedetection requirement.

Optionally, the method may further comprise an initialization stepbefore the step S10 to set the parameters involved in the method; forexample, the specified value δ may be set; other parameters to be setmay be determined according to the specific embodiment; that step may beneglected if the parameter values are fixed to default values.

Optionally, the method may further comprise an output step after thejudgment step S40, i.e., recording the estimated upper switching valueand estimated lower switching value obtained in the last cycle as upperswitching value and lower switching value of the pressure switch 8 inthe controller 5, and transmitting the result to the external device.

Different variants of the implementation process of the above-mentionedsteps may be possible, according to different embodiments.

The method may be used to detect the upper switching value or lowerswitching value of a pressure switch 8 separately, and may also be usedto detect the upper switching value and lower switching value of apressure switch 8 at the same time.

Hereunder three different embodiments (embodiments 3-5) will beintroduced in detail, in an example in which the upper switching valueand lower switching value of a pressure switch are detected at the sametime and the difference between a maximum value and a minimum valuebetween the estimated switching values acquired in the last two times iscompared with the specified value δ.

Embodiment 3: Constant Rate Pressure Control Method Based on PolynomialFitting

FIG. 1 shows a device for detecting the switching value of a pressureswitch. The pressure in the pressure pipeline 3 is changed at anapproximately constant pressurization rate and depressurization rate inthe detection process. The detection process comprises the followingsteps:

Initial value acquisition step: the pressure generator 1 changes thepressure in the pressure pipeline 3 at a high pressurization rate ordepressurization rate, till ON-OFF state switching of the pressureswitch 8 is detected; at that point, the pressure sensor 4 acquires thepressure value in the pressure pipeline 3 as an initial upper switchingvalue R₀ or initial lower switching value F₀ and the correspondinginitial pressurization rate v₁₀ or initial depressurization rate v₂₀ atthe time of state switching of the pressure switch 8, and the acquiredvalues are stored in the controller 5.

Detected value acquisition step: the pressure generator 1 increases thepressure in the pressure pipeline 3 from the lower switching valueF_((i-1)) at a pressurization rate V_(i)=θV_(1(i-1)), the upperswitching value acquired by the pressure sensor 4 at the time of stateswitching of the pressure switch 8 is taken as a detected upperswitching value R_(i), and the pressurization rate v_(1i) at the time ofstate switching of the pressure switch 8 is acquired; the pressuregenerator 1 decreases the pressure in the pressure pipeline 3 from theupper switching value R_(i) at a depressurization rate V_(i)θV_(2(i-1)),the lower switching value acquired by the pressure sensor 4 at the timeof state switching of the pressure switch 8 is taken as a detected lowerswitching value F_(i), the pressurization rate v_(2i) at the time ofstate switching of the pressure switch 8 is acquired, and the acquiredvalues are stored in the controller 5, where, i is the cycle index, θ isthe rate adjustment factor, and i=1,2,3 . . . 0<θ<1.

Estimated value acquisition step: if i≥1, fitting estimation isperformed for the detected upper switching values R_(i) (including theinitial upper switching value R₀) acquired in the last two times, and anestimated upper switching value {circumflex over (R)}_(r) of thepressure switch is acquired; in addition, fitting estimation isperformed for the detected lower switching values F_(i) (including theinitial lower switching value F₀) acquired in the last two times, and anestimated lower switching value

of the pressure switch is acquired; otherwise the cycle index i isincremented by 1, and the process turns to the detected valueacquisition step, where, r is the estimation index, and =1,2,3 . . . .

Judgment step: If r≥2 and the following criterion is met:

max(

⁻¹,

_(r))−min(

_(r-1),

_(r))<δ and max(

_(r-1),

_(r))−min(

_(r-1),

_(r))<δ, then the detection is terminated, the estimated upper switchingvalue and estimated lower switching value obtained in the last cycle aretaken as upper switching value and lower switching value of the pressureswitch 8 and stored in the controller 5, and the loop is exited;otherwise the cycle index i is incremented by 1, the estimation index ris incremented by 1, and the process turns to the detected valueacquisition step, wherein, the value range of the specified value δ is0.2-0.5 times of the accuracy of the pressure switch 8.

In the above method, if the parameters (e.g., specified value δ and therate adjustment factor θ) are to be set again, the embodiment mayfurther comprise an initialization step; if the device is connected toan external device, the embodiment 3 may further comprise an outputstep.

In the above method, the number of cycles depends on the presetspecified value δ, rate adjustment factor θ, and initial pressurizationrate v₁₀ and/or initial depressurization rate v₂₀, etc.; in the detectedvalue acquisition step of the method, the higher the rate adjustmentfactor θ is, the less the pressurization rate or depressurization rateis decreased in each time of detection, and thereby the shorter therequired time is; however, in such a case, usually the times ofdetection required to reach required accuracy will be increased, and thetotal detection time will be longer accordingly; in contrast, the lowerthe rate adjustment factor θ is, the more the pressurization rate ordepressurization rate is decreased in each time of detection;accordingly, usually the times of detection will be reduced, but theexecution time in each time of detection will be longer. A trade-offmust be made for the actual detection. Usually the specified value δ isset with reference to the nominal value of the pressure switch and therequirement for accuracy in the application scenario, and the valuerange may be 0.2-0.5 times of the accuracy of the pressure switch 8; thevalue range of the specified value δ being 0.2-0.5 times of the accuracyof the pressure switch 8 means that the specified value δ may be a fixedvalue or non-fixed value within a range of 0.2-0.5 times of the accuracyof the pressure switch 8; for example, the specified values δ used inthe judgment steps in two detection processes may be different from eachother.

Embodiment 4: Variable Rate Pressure Control Method Based on PolynomialFitting

In order to further reduce the detection time while meeting therequirement for the repeatability index 15, the above-mentionedembodiment 3 of the method is improved by using real-time varyingpressurization rate and depressurization rate in each time of detection,i.e., the pressure change rate is higher when the pressure is fartherfrom the state switching point of the pressure switch, so as to savetime; the pressure change rate is lower when the pressure is closer tothe state switching point of the pressure switch, to reduce thedetection error. In the detection process, the process from the time thepressure sensor 4 reads the pressure value in the pressure pipeline 3 tothe next time the pressure sensor 4 reads the pressure value in thepressure pipeline 3 is used as a detection step; the process throughwhich the detection of an upper switching value and an lower switchingvalue of the pressure switch is accomplished is used as a cycle.

The steps included in the variable rate pressure control method in theembodiment 4 are essentially the same as the steps in the embodiment 3,except the rules under which the pressure generator 1 changes thepressure in the pressure pipeline 3 in the detected value acquisitionstep.

The detected value acquisition step in the embodiment 4 is as follows:Detected value acquisition step: the pressure generator 1 increases thepressure in the pressure pipeline 3 from the lower switching valueF_(i-1) at a pressurization rate V_(ij)=θv_(1(i-1))+k(R_(i-1)−p_(j)),the upper switching value acquired by the pressure sensor 4 at the timeof state switching of the pressure switch 8 is taken as a detected upperswitching value R_(i), and the pressurization rate v_(1i) at the time ofstate switching of the pressure switch 8 is acquired, where, i is thecycle index, i=1,2,3, . . . , j is the detection step index, j=1,2,3, .. . , k is the pressure adjustment factor, θ is the rate adjustmentfactor, 0<k, and 0<θ<1; p_(j) is the pressure value detected by thepressure sensor unit 3 in the detection step j; v_((i-1)) is thepressurization rate or initial pressurization rate at the time thedetected upper switching value is acquired in the detected valueacquisition step (i−1), and R_(i-1) is the detected upper switchingvalue or initial upper switching value detected in the detected valueacquisition step i−1;

the pressure generator 1 decreases the pressure in the pressure pipeline3 from the detected upper switching value R_(i) at a depressurizationrate V_(ij)=θv_(2(i-1))+k(p_(j)−F_(i-1)), the lower switching valueacquired by the pressure sensor 4 at the time of state switching of thepressure switch 8 is taken as a detected lower switching value F_(i),and the pressurization rate v_(2i) at the state switching of thepressure switch 8 is acquired; and the acquired values are stored in thecontroller 5; where, p_(j) is the pressure value detected by thepressure sensor unit 3 in the detection step j; v_(2(i-1)) is thedepressurization rate or initial depressurization rate at the time ofstate switching of the pressure switch 8 in the detected valueacquisition step (i−1), and F_(i-1) is the detected lower switchingvalue or initial lower switching value detected in the detected valueacquisition step i−1.

Likewise, this embodiment may further comprise an initialization stepand/or an output step.

The pressure in the pressure pipeline 3 is changed at a real-timevarying pressurization rate or depressurization rate, the detected upperswitching value or detected lower switching value of the pressure switchis detected, and the pressure adjustment factor k is a fixed valuegreater than zero. Likewise, usually the specified value δ is set withreference to the nominal value of the pressure switch and therequirement for accuracy in the application scenario, and the valuerange may be 0.2-0.5 times of the accuracy of the pressure switch 8; thevalue range of the specified value δ being 0.2-0.5 times of the accuracyof the pressure switch 8 means that the specified value δ may be a fixedvalue or non-fixed value within a range of 0.2-0.5 times of the accuracyof the pressure switch 8; for example, the specified values δ used inthe judgment steps in two detection processes may be different from eachother.

The method can further reduce the detection time so that the detectedupper switching value or detected lower switching value approaches thetrue value quickly and achieves high consistency.

Embodiment 5: Fuzzy Pressure Control Method

In this embodiment, the controller 5 provide an instructive guidelinefor pressure increase/decrease in the pressure pipeline according to thepressure value acquired by the pressure sensor 4 and the stateinformation of the pressure switch 8; the operator may operate thepressure generator 1 to accomplish the pressurization anddepressurization process under the guidelines provided by the controller5. The upper rate limit is divided into different rate ranges accordingto the upper limit of pressurization or depressurization of the pressureswitch 8. For example, the guideline may be a fuzzy guideline, such as“low pressurization rate,” “medium pressurization rate,” “highpressurization rate,” “low depressurization rate,” “mediumdepressurization rate,” or “high depressurization rate,” etc.

Specifically, the method employs the device for detecting the switchingvalue of a pressure switch shown in FIG. 1 or 10. In the detectionprocess, the operator operates the pressure generator 1 under theguideline provided by the controller 5 to change the pressure in thepressure pipeline 3. The process comprises the following steps:

Initial value acquisition step: the pressure generator 1 is operated tochange the pressure in the pressure pipeline 3 at a high pressurizationrate or depressurization rate, till state switching of the pressureswitch 8 is detected; at that point, the pressure sensor 4 acquires thepressure value in the pressure pipeline 3 as an initial upper switchingvalue R₀ or initial lower switching value F₀ and the correspondinginitial pressurization rate v₁₀ or initial depressurization rate v₂₀ atthe time of state switching of the pressure switch 8, and the acquiredvalues are stored in the controller 5.

Detected value acquisition step: the pressure generator 1 is operated toincrease the pressure in the pressure pipeline 3 from the lowerswitching value F_((i-1)) under a fuzzy guideline provided by thecontroller 5, the upper switching value acquired by the pressure sensor4 at the time of state switching of the pressure switch 8 is taken as adetected upper switching value R_(i), and the pressurization rate v_(1i)at the time of state switching of the pressure switch 8 is acquired; thepressure generator 1 decreases the pressure in the pressure pipeline 3from the upper switching value R_(i) under the fuzzy guideline providedby the controller 5, the lower switching value acquired by the pressuresensor 4 at the time of state switching of the pressure switch 8 istaken as a detected lower switching value F_(i), the pressurization ratev_(2i) at the time of state switching of the pressure switch 8 isacquired, and the acquired values are stored in the controller 5, where,i is the cycle index, θ is the rate adjustment factor, and i=1,2,3 . . ..

Estimated value acquisition step: if i≥1, fitting estimation isperformed for the detected upper switching values R_(i) (including theinitial upper switching value R₀) acquired in the last two times, and anupper switching value

of the pressure switch is acquired; in addition, fitting estimation isperformed for the detected lower switching values F_(i) (including theinitial lower switching value F₀) acquired in the last two times, and anestimated lower switching value

_(r) of the pressure switch is acquired; otherwise the cycle index i isincremented by 1, and the process turns to the detected valueacquisition step, where, r is the estimation index, and r=1,2,3 . . . .

Judgment step: If r≥2 and the following criterion is met:

max(

_(r-1),

_(r))−min(

_(r-1),

_(r))<δ and max(

_(r-1),

_(r))−min(

_(r-1),

_(r))<δ, then the detection is terminated, the estimated upper switchingvalue and estimated lower switching value obtained in the last cycle aretaken as upper switching value and lower switching value of the pressureswitch 8 and stored in the controller 5, and the loop is exited;otherwise the cycle index i is incremented by 1, the estimation index ris incremented by 1, and the process turns to the detected valueacquisition step, wherein, the value range of the specified value δ is0.2-0.5 times of the accuracy of the pressure switch 8.

In the above method, if the parameters (e.g., specified value δ and therate adjustment factor θ) are to be set again, the embodiment mayfurther comprise an initialization step; if the device is connected toan external device 9, the embodiment may further comprise an outputstep.

Both Embodiment 3 and Embodiment 4 require the pressure generator 1 toexercise real-time control of the pressure in the pressure pipeline at apressurization rate or depressurization rate provided by the controller5, and usually require automatic measurement and control devices. Theyhave advantages of quick, accurate control and convenience. Embodiment 5is a simple implementation of the device described in the presentinvention, and it can also realize accurate measurement of the switchingvalue of a pressure switch with the method in the present invention. Itcan work with most of existing pressure generators, and has advantagesof simplicity, high practicality and low cost.

Embodiments

Hereunder experimental verification was carried out for the embodimentsfor detecting the switching value of a pressure switch according to thepresent invention. The tested pressure switch is a CATO pressure switchmodel PN30-P060G14H3AQ, the specific parameter indicators of which areshown in Table 1.

TABLE 1 List of Parameters of Tested Pressure Switch Tested Object CATOelectronic pressure switch Model PN30-P060G14H3AQ Scale (kPa) 6000Accuracy 0.5% f.s (0.5% scale)

In the experiments, the above-mentioned CATO pressure switch was used asthe tested object. In the initial value acquisition step, pressure wasincreased or decreased at a fixed initial pressurization rate ordepressurization rate of about 300 kPa/s, and thereby an initial upperswitching value was obtained; the rate adjustment factor θ was within arange of 0.4˜0.6, the pressure adjustment factor k was about 0.5, andthe specified value δ was set to 6 kPa (0.1% scale).

The detection results in the embodiment 1 and embodiment 2 are shown inTables 2 and 3, and the relation between pressure change rate anddetected pressure switching value is shown in FIG. 5. As shown in Tables2 and 3, in the embodiment 1, the pressure in the pressure pipeline 3was increased or decreased at a constant rate with a constant ratepressure control method, an upper switching value equal to 4,066 kPa wasdetected through 5 cycles, and the time consumed was 68.3 s; a lowerswitching value equal to 3,858 kPa was detected through 6 cycles, andthe time consumed was 162.3 s; in the embodiment 2, a variable ratepressure control method was used, an upper switching value equal to4,066 kPa was obtained through 6 cycles, and the time consumed was 33.7s; a lower switching value equal to 3,852 kPa was detected through 6cycles, and the time consumed was 53.5 s; in addition, the change rateat the time of state switching of the pressure switch 8 when thedetection loop was terminated was reduced to a lower rate, and thedifference between the detection results of the two embodiment issmaller than the specified value δ (6 kPa), which ensures the accuracyof the detection results; obviously, in the initial stage, the pressurescanning range is reduced from 0˜6,000 kPa to about 3,620μ4,300 kPaquickly at a high pressure change rate (300 kPa/s), and thereby thedetection time is shortened; in the embodiment 2, a variable rate methodis used to accelerate the measurement process when the pressure is farfrom the switching value, and thereby the required detection time wasmuch further reduced.

TABLE 2 Detection Result of Upper Switching Values in Embodiment 1 andEmbodiment 2 Embodiment 1 Embodiment 2 Initial upper Initial upperswitching switching Pressurization value or Pressurization value or rateν_(1i) at detected upper rate ν_(1i) at detected upper upper switchingTime upper switching Time Detection switching value R_(i) expendedswitching value R_(i) expended process value (kPa/s) (kPa) (s) value(kPa/s) (kPa) (s) Initial value 304.89 4274 2.9 313.15 4299 3.7acquisition step: acquired initial value, i = 0 Detected value 126.144148 10.8 150.50 4186 10.1 acquisition step: detected value acquired inthe first cycle, i = 1 Detected value 63.64 4101 21.7 77.10 4129 16.4acquisition step: detected value acquired in the second cycle, i = 2Detected value 31.95 4075 39.2 43.96 4093 24.1 acquisition step:detected value acquired in the third cycle, i = 3 Detected value 15.184066 68.3 25.97 4076 33.7 acquisition step: detected value acquired inthe fourth cycle, i = 4 Detected value 15.05 4066 45.5 acquisition step:detected value acquired in the fifth cycle, i = 5 Judgment step: 406668.3 4066 33.7 acquired switching value of pressure switch

TABLE 3 Detection Result of Lower Switching Values in Embodiment 1 andEmbodiment 2 Embodiment 1 Embodiment 2 Initial lower Initial lowerswitching switching value or value or Depressurization detected lowerDepressurization detected lower rate ν_(2i) at switching Time rateν_(2i) at switching Time Detection lower switching value F_(i) expendedlower switching value F_(i) expended process value (kPa/s) (kPa) (s)value (kPa/s) (kPa) (s) Initial value −303.473 3653 5.8 −310.806 36217.4 acquisition step: acquired initial value, i = 0 Detected value−124.262 3775 15.1 −138.595 3736 13.2 acquisition step: detected valueacquired in the first cycle, i = 1 Detected value −60.0587 3815 28.6−73.478 3794 20.4 acquisition step: detected value acquired in thesecond cycle, i = 2 Detected value −30.8414 3839 50.6 −37.4146 3825 29.3acquisition step: detected value acquired in the third cycle, i = 3Detected value −16.6224 3850 89.9 −21.4674 3842 40.2 acquisition step:detected value acquired in the fourth cycle, i = 4 Detected value−7.15904 3858 162.3 −9.62977 3852 53.5 acquisition step: detected valueacquired in the fifth cycle, i = 5 Judgment step: 3858 162.3 3852 53.5acquired switching value of pressure switch

The detection results in the embodiment 3 are shown in Tables 4 and 5,and the relation between pressure change rate and detected pressureswitching value is shown in FIG. 6; the detection results in theembodiment 4 are shown in Tables 6 and 7, and the relation betweenpressure change rate and detected pressure switching value is shown inFIG. 7; the detection results in the embodiment 5 are shown in Tables 8and 9, and the relation between pressure change rate and detectedpressure switching value is shown in FIG. 8.

As shown in Tables 4 and 7, in the embodiment 3, the pressure in thepressure pipeline 3 was increased or decreased at a constant rate with aconstant rate pressure control method, an upper switching value equal to4,049 kPa was detected through 4 cycles, and the time consumed was 39.2s; a lower switching value equal to 3,863 kPa was detected through 5cycles, and the time consumed was 89.9 s; in the embodiment 4, avariable rate pressure control method was used to increase or decreasethe pressure in the pressure pipeline 3, an upper switching value equalto 4,051 kPa was obtained through 5 cycles, and the time consumed was33.7 s; a lower switching value equal to 3858 kPa was detected through 4cycles, and the time consumed was 29.3 s; in the two embodiments, thechange rate at the time of state switching of the pressure switch 8 whenthe detection loop was terminated was reduced to a lower rate, and thedifference between the detection results of the two embodiment wassmaller than the specified value δ (i.e., 6 kPa), which ensures theaccuracy of the detection results; obviously, in the initial stage, thepressure scanning range was reduced from 0˜6,000 kPa to about3,620˜4,300 kPa quickly at a high pressure change rate (300 kPa/s), andthereby the detection time was shortened; in the embodiment 4, avariable rate method was used to accelerate the measurement process whenthe pressure was far from the switching value, and thereby the requireddetection time was further shortened greatly.

In the traditional manual detection method for detecting the switchingvalue of the pressure switch 8, there is no specific requirement for thepressure change rate when the switching value of the pressure switch isdetected. Consequently, it is difficult to ensure the uniformity andaccuracy of the detection result on the basis of experience (see thedetected switching value in the embodiment 5).

In the embodiment 5, a fuzzy pressure control method is used to increaseor decrease the pressure in the pressure pipeline 3. With that method,it is unnecessary to gradually decrease the pressurization rate ordepressurization rate, and the requirements for the operator are lower.The method is simpler to implement. As shown in Tables 8 and 9, an upperswitching value equal to 4,050 kPa can be detected only through 3cycles, and a lower switching value 3,859 kPa can be detected through 4cycles. The difference between the result in this embodiment and theresults in the embodiments 3 and 4 is smaller than the specified valueδ, which ensures the accuracy of the detection result.

TABLE 4 Detection Result of Upper Switching Value in Embodiment 3Embodiment 3 Initial upper Pressuri- switching zation value or ratev_(1i) at detected Estimated upper upper upper switching switchingswitching Time value value R_(i) value  

expended Detection process (kPa/s) (kPa) (kPa) (s) Initial value 304.894274 2.9 acquisition step: acquired initial value, i = 0 Detected value126.14 4148 4059 10.8 acquisition step and estimated value acquisitionstep: value acquired in the first cycle, i = 1 Detected value 63.64 41014052 21.7 acquisition step and estimated value acquisition step: valueacquired in the second cycle, i = 2 Detected value 31.95 4075 4049 39.2acquisition step and estimated value acquisition step: value acquired inthe third cycle, i = 3 Judgment step: 4049 39.2 acquired switching valueof pressure switch

TABLE 5 Detection Result of Lower Switching Value in Embodiment 3Embodiment 3 Initial lower Depressur- switching ization value ratev_(2i) at or detected Estimated lower lower lower Time switchingswitching switching ex- value value F_(i) value  

pended Detection process (kPa/s) (kPa) (kPa) (s) Initial valueacquisition −303.473 3652.97 5.8 step: acquired initial value, i = 0Detected value −124.262 3775.46 3860 15.1 acquisition step and estimatedvalue acquisition step: value acquired in the first cycle, i = 1Detected value −60.0587 3815.41 3853 28.6 acquisition step and estimatedvalue acquisition step: value acquired in the second cycle, i = 2Detected value −30.8414 3839.32 3865 50.6 acquisition step and estimatedvalue acquisition step: value acquired in the third cycle, i = 3Detected value −16.6224 3850.10 3863 89.9 acquisition step and estimatedvalue acquisition step: value acquired in the fourth cycle, i = 4Judgment step: acquired 3863 89.9 switching value of pressure switch

TABLE 6 Detection Result of Upper Switching Value in Embodiment 4Embodiment 4 Initial upper Pressuri- switching zation value or Estimatedrate v_(1i) at detected upper upper upper switching switching switchingTime value value R_(i) value  

 _(r) expended Detection process (kPa/s) (kPa) (kPa) (s) Initial value313.15 4299 3.7 acquisition step: acquired initial value, i = 0 Detectedvalue 150.50 4186 4081 10.1 acquisition step and estimated valueacquisition step: value acquired in the first cycle, i = 1 Detectedvalue 77.10 4129 4070 16.4 acquisition step and estimated valueacquisition step: value acquired in the second cycle, i = 2 Detectedvalue 43.96 4093 4046 24.1 acquisition step and estimated valueacquisition step: value acquired in the third cycle, i = 3 Detectedvalue 25.97 4076 4051 33.7 acquisition step and estimated valueacquisition step: value acquired in the fourth cycle, i = 4 Judgmentstep: 4051 33.7 acquired switching value of pressure switch

TABLE 7 Detection Result of Lower Switching Value in Embodiment 4Embodiment 4 Initial lower Depressuri- switching zation value or ratev_(2i) at detected Estimated lower lower lower switching switchingswitching Time value value F_(i) value  

 _(r) expended Detection process (kPa/s) (kPa) (kPa) (s) Initial valueacquisition −310.806 3621 7.4 step: acquired initial value, i = 0Detected value −138.595 3736 3828 13.2 acquisition step and estimatedvalue acquisition step: value acquired in the first cycle, i = 1Detected value −73.478 3794 3859 20.4 acquisition step and estimatedvalue acquisition step: value acquired in the second cycle, i = 2Detected value −37.4146 3825 3858 29.3 acquisition step and estimatedvalue acquisition step: value acquired in the third cycle, i = 3Judgment step: acquired 3858 29.3 switching value of pressure switch

TABLE 8 Detection Result of Upper Switching Value in Embodiment 5Embodiment 5 Initial upper switching Pressurization value or rate V_(1i)at detected Estimated upper upper upper switching switching switchingvalue value R_(i) value  

_(r) Detection process (kPa/s) (kPa) (kPa) Initial value acquisition313.15 4299.11 step: acquired initial value, i = 0 Detected valueacquisition 15.05 4065.59 4054 step and estimated value acquisitionstep: value acquired in the first cycle, i = 1 Detected valueacquisition 77.10 4129.45 4050 step and estimated value acquisitionstep: value acquired in the second cycle, i = 2 Judgment step: acquired4050 switching value of pressure switch

TABLE 9 Detection Result of Lower Switching Value in Embodiment 5Embodiment 5 Initial lower switching value or detected EstimatedDepressurization lower lower rate v_(2i) at lower switching switchingswitching value value F_(i) value  

 _(r) Detection process (kPa/s) (kPa) (kPa) Initial value acquisition−9.63 3851.53 step: acquired initial value, i = 0 Detected valueacquisition −37.41 3825.00 3861 step and estimated value acquisitionstep: value acquired in the first cycle, i = 1 Detected valueacquisition −310.81 3620.53 3853 step and estimated value acquisitionstep: value acquired in the second cycle, i = 2 Detected valueacquisition −21.47 3842.40 3859 step and estimated value acquisitionstep: value acquired in the third cycle, i = 3 Judgment step: acquired3859 switching value of pressure switch

INDUSTRIAL APPLICABILITY

The present invention provides a device for detecting the switchingvalue of a pressure switch, which can accomplish the detection of theswitching value of a pressure switch, and is suitable for industrialmanufacturing; the switching value of a pressure switch can be detectedwith the device through cyclic detection. The device not only realizesrapid detection, but also achieves high consistency and high accuracy,and is convenient to use and suitable for industrial application.

The invention claimed is:
 1. A method for detecting a switching value ofa pressure switch with a detection device, wherein, the detection devicecomprises a pressure generator that communicates with the pressureswitch via a pressure pipeline, a pressure control element, a pressuresensor, and a controller with a data processing unit, wherein, thepressure sensor is installed on the pressure pipeline and electricallyconnected to the controller, the pressure control element iselectrically connected to the pressure generator, configured to controlthe pressure generator, and electrically connected to the controller,the data processing unit of the controller is electrically connected tothe pressure sensor and the pressure switch to acquire, analyze andprocess data, generate a corresponding control command, and transmit thecontrol command via the pressure control element to the pressuregenerator, so as to adjust the pressure value in the pressure pipelineand thereby cause ON-OFF state switching of the pressure switch; theswitching value of the pressure switch being detected with the methodfor detecting the switching value of a pressure switch; the method fordetecting the switching value of the pressure switch comprising thefollowing steps: an initial value acquisition step: acquiring, via thepressure sensor, a pressure value of the pressure switch as an initialupper switching value R₀ and a corresponding pressurization rate as aninitial pressurization rate v₁₀ at the time of state switching of thepressure switch in a pressurization process of the pressure switch, oracquiring, via the pressure sensor, a pressure value of the pressureswitch as an initial lower switching value F₀ and a correspondingdepressurization rate as an initial depressurization rate v₂₀ at thetime of state switching of the pressure switch in a depressurizationprocess of the pressure switch, by the data processing unit of thecontroller; a detected value acquisition step: transmitting, via thepressure control element, a command for adjusting (increasing ordecreasing) the pressure in the pressure pipeline to the pressuregenerator, acquiring, via the pressure sensor, a pressure value of thepressure switch as a detected upper switching value R_(i) and acorresponding pressurization rate v_(1i) at the time of state switchingof the pressure switch in the pressurization process of the pressureswitch, or acquiring, via the pressure sensor, a pressure value as adetected lower switching value F_(i) and a correspondingdepressurization rate v_(2i) at the time of state switching of thepressure switch in the depressurization process of the pressure switchby the data processing unit, where i=1,2,3 . . . ; a judgment step:comparing a difference between a maximum value and a minimum valuebetween/among the detected upper switching values (including the initialupper switching value) or the detected lower switching values (includingthe initial lower switching value) that were acquired in the last two ormore times with a specified value δ, by the data processing unit, andreturning to the detected value acquisition step if the difference isgreater than or equal to the specified value δ; or taking the detectedupper switching value or detected lower switching value that wasacquired in the last time as the upper switching value or lowerswitching value of the pressure switch and outputting that value, by thedata processing unit, if the difference is smaller than the specifiedvalue δ; wherein, in the detected value acquisition step, thepressurization rate or depressurization rate is decreased from apressurization rate v_(1(i-1)) or depressurization rate v_(2(i-1)) in alast time of state switching of the pressure switch, a rate adjustmentvalue is added to the decreased pressurization rate or depressurizationrate, and the resultant pressurization rate or depressurization rate isused to change the pressure in the pipeline; wherein, in the detectedvalue acquisition step, the rate adjustment value is decreased as thepressure value in the pressure pipeline is closer to the detected upperswitching value (including the initial upper switching value) or thedetected lower switching value (including the initial lower switchingvalue) that was acquired in the last time; and wherein, the rateadjustment value is a function of the pressure value in the pipelineexpressed by ΔV_(ij)=k(R_(i-1)−p_(j)), and the pressurization rate isexpressed by V_(ij)=θv_(1(i-1))+ΔV_(ij), where, ΔV_(ij) is the rateadjustment value in detection step j in the detected value acquisitionstep i, V_(ij) is the pressurization rate in the detected valueacquisition step i, v_(1(i-1)) is the pressurization rate when thedetected upper switching value was acquired in the detected valueacquisition step (i−1), R_(i-1) is the detected upper switching valuedetected in the detected value acquisition step (i−1), p_(j) is thepressure value in the pressure pipeline detected in the detection stepj, k is a pressure adjustment factor, θ is a rate adjustment factor, andk≥0, 0<θ<1, i=1,2,3, . . . , j=1, 2,3 . . . .
 2. The method fordetecting the switching value of the pressure switch according to claim1, wherein, the controller further comprises a storage unit, which iselectrically connected to and interacts with the pressure controlelement and the pressure sensor, and has an interface with the dataprocessing unit for data interaction; the data processing unit havingdata interaction with the storage unit.
 3. The method for detecting theswitching value of the pressure switch according to claim 1, wherein thedetection device further comprises an electrical interface electricallyconnected to the controller, wherein the pressure switch transmits aswitching action signal of the pressure switch to the controller via theelectrical interface.
 4. The method for detecting the switching value ofthe pressure switch according to claim 3, wherein the detection devicefurther comprises an external device connected to the controller via theelectrical interface, wherein the electrical interface is an integratedcomponent that has different interfaces, including a digital signalinterface, a USB interface, a serial interface, a wireless interface andan Ethernet interface, and the external device may be one or more of acomputer, a liquid crystal display (LCD) and a touch screen.
 5. Themethod for detecting the switching value of the pressure switchaccording to claim 1, wherein, in the detected value acquisition step,the data processing unit acquires a detected upper switching value R_(i)and a pressurization rate v_(1i) at the time of state switching of thepressure switch or acquires a detected lower switching value F_(i) and adepressurization rate v_(2i) at the time of state switching of thepressure switch via the pressure sensor, in a way that ensure thepressurization rate or depressurization rate at the time of stateswitching of the pressure sensor is smaller than the pressurization ratev_(1(i−1)) or depressurization rate v_(2(i−1)) in the last time of stateswitching of the pressure switch.
 6. The method for detecting theswitching value of the pressure switch according to claim 1, furthercomprising an estimated value acquisition step after the detected valueacquisition step, wherein, in the estimated value acquisition step, thedata processing unit performs fitting estimation for the detected upperswitching values (including the initial upper switching value) or thedetected lower switching values (including the initial lower switchingvalue) that were acquired in the last two or more times, and acquires anestimated upper switching value

or estimated lower switching value

of the pressure switch, where r=1,2,3 . . . .
 7. The method fordetecting the switching value of the pressure switch according to claim6, wherein, in the estimated value acquisition step, fitting estimationis performed for the relation between detected upper switching value andpressurization rate or between detected lower switching value anddepressurization rate with a polynomial fitting method based on leastsquare, and a corresponding estimated switching value when thepressurization rate or depressurization rate of zero is taken as theestimated upper switching value or estimated lower switching value. 8.The method for detecting the switching value of the pressure switchaccording to claim 6, wherein, in the judgment step, the differencebetween a maximum value and a minimum value between/among the estimatedupper switching values or estimated lower switching values acquired inthe last two or more times is compared with a specified value δ, and theprocess returns to the detected value acquisition step if the differenceis greater than or equal to the specified value δ; or the estimatedupper switching value or the estimated lower switching value acquired inthe last time is taken as the upper switching value or lower switchingvalue of the pressure switch, if the difference is smaller than thespecified value δ.
 9. The method for detecting the switching value ofthe pressure switch according to claim 1, wherein, in the judgment step,the specified value δ is a preset accuracy, and its value is within arange of 0.2-0.5 times of the accuracy of the pressure switch.
 10. Themethod for detecting the switching value of the pressure switchaccording to claim 1, wherein, in the initial value acquisition step,the pressure in the pressure pipeline changes at a high pressurizationrate or depressurization rate, until ON-OFF state switching of thepressure switch is detected; at that point, the pressure value at thetime of state switching of the pressure switch is acquired as an initialupper switching value R_(i) or initial lower switching value F_(i) andthe pressurization rate or depressurization rate at the time of stateswitching of the pressure switch is taken as the initial pressurizationrate v_(1i) or initial depressurization rate v_(2i).
 11. A method fordetecting a switching value of a pressure switch with a detectiondevice, wherein, the detection device comprises a pressure generator, apressure sensor, and a pressure pipeline, the pressure generator and thepressure sensor communicate with the pressure switch through thepressure pipeline, the pressure value in the pressure pipeline isadjusted via the pressure generator, so that the pressure switch isswitched between an ON state and an OFF state, and the detection devicedetects the switching value of the pressure switch with the method fordetecting the switching value of the pressure switch, the method fordetecting the switching value of the pressure switch comprises thefollowing steps: an initial value acquisition step: acquiring a pressurevalue of the pressure switch as an initial upper switching value R₀ anda corresponding pressurization rate as an initial pressurization ratev₁₀ at the time of state switching of the pressure switch in apressurization process of the pressure switch, or acquiring a pressurevalue of the pressure switch as an initial lower switching value F₀ anda corresponding depressurization rate as an initial depressurizationrate v₂₀ at the time of state switching of the pressure switch in adepressurization process of the pressure switch; a detected valueacquisition step: acquiring a pressure value as a detected upperswitching value R_(i) v_(1(i−1)) and a corresponding pressurization ratev_(1i) v_(2(i−1)) at the time of state switching in a pressurizationprocess of the pressure switch, or acquiring a pressure value as adetected lower switching value F_(i) R_(i) and a correspondingdepressurization rate v_(2i) v_(1i) at the time of state switching in adepressurization process of the pressure switch, in a way that ensuresthe pressurization rate or depressurization rate at the time of stateswitching of the pressure switch is smaller than the pressurization ratev_(1(i−1)) F_(i) or depressurization rate v_(2(i−1)) v_(2i) in a lasttime of state switching of the pressure switch, where i=1,2,3 . . . ; ajudgment step: comparing a difference between a maximum value and aminimum value between/among the detected upper switching values(including the initial upper switching value) or the detected lowerswitching values (including the initial lower switching value) that wereacquired in the last two or more times with a specified value δ, andreturning to the detected value acquisition step if the difference isgreater than or equal to the specified value δ; or taking the detectedupper switching value or detected lower switching value that wasacquired in the last time as the upper switching value or lowerswitching value of the pressure switch, if the difference is smallerthan the specified value δ; wherein, in the detected value acquisitionstep, the pressurization rate or depressurization rate is decreased froma pressurization rate v_(1(i−1)) or depressurization rate v_(2(i−1)) inthe last time of state switching of the pressure switch, a rateadjustment value is added to the decreased pressurization rate ordepressurization rate, and the resultant pressurization rate ordepressurization rate is used to change the pressure in the pipeline;wherein, in the detected value acquisition step, the rate adjustmentvalue is decreased as the pressure value in the pressure pipeline iscloser to the detected upper switching value (including the initialupper switching value) or the detected lower switching value (includingthe initial lower switching value) that was acquired in the last time;and wherein, the rate adjustment value is a function of the pressurevalue in the pipeline expressed by ΔV_(ij)=k(R_(i-1)−p_(j)), and thepressurization rate is expressed by V_(ij)=θv_(1(i−1))+ΔV_(ij), where,ΔV_(ij) is the rate adjustment value in detection step j in the detectedvalue acquisition step i, V_(ij) is the pressurization rate in thedetected value acquisition step i, v_(1(i−1)) is the pressurization ratewhen the detected upper switching value was acquired in the detectedvalue acquisition step (i−1), R_(i-1) is the detected upper switchingvalue detected in the detected value acquisition step (i−1), p_(j) isthe pressure value in the pressure pipeline detected in the detectionstep j, k is a pressure adjustment factor, θ is a rate adjustmentfactor, and k≥0, 0<θ<1, i=1,2,3, . . . , j=1,2,3, . . . .
 12. The methodfor detecting the switching value of the pressure switch according toclaim 11, wherein, in the judgment step, the specified value δ is apreset accuracy, and its value is within a range of 0.2-0.5 times of theaccuracy of the pressure switch.
 13. The method for detecting theswitching value of the pressure switch according to claim 11, wherein,in the initial value acquisition step, the pressure in the pressurepipeline changes at a high pressurization rate or depressurization rate,until ON-OFF state switching of the pressure switch is detected; at thatpoint, the pressure value at the time of state switching of the pressureswitch is acquired as an initial upper switching value R_(i) or initiallower switching value F_(i), and the pressurization rate ordepressurization rate at the time of state switching of the pressureswitch is taken as the initial pressurization rate v_(1i) or initialdepressurization rate v_(2i).
 14. A method for detecting a switchingvalue of a pressure switch with a detection device, wherein, thedetection device comprises a pressure generator, a pressure sensor, anda pressure pipeline, the pressure generator and the pressure sensorcommunicate with the pressure switch through the pressure pipeline, thepressure value in the pressure pipeline is adjusted via the pressuregenerator, so that the pressure switch is switched between an ON stateand an OFF state, and the detection device detects the switching valueof the pressure switch with the method for detecting the switching valueof the pressure switch, the method for detecting the switching value ofthe pressure switch comprises the following steps: an initial valueacquisition step for acquiring a pressure value of the pressure switchas an initial upper switching value R₀ and a correspondingpressurization rate as an initial pressurization rate v₁₀ at the time ofstate switching of the pressure switch in a pressurization process ofthe pressure switch, or acquiring a pressure value of the pressureswitch as an initial lower switching value F₀ and a correspondingdepressurization rate as an initial depressurization rate v₂₀ at thetime of state switching of the pressure switch in a depressurizationprocess of the pressure switch; a detected value acquisition step foracquiring a pressure value as a detected upper switching value R_(i) anda corresponding pressurization rate v_(1i) at the time of stateswitching of the pressure switch in a pressurization process of thepressure switch, or acquiring a pressure value as a detected lowerswitching value F_(i) and a corresponding depressurization rate v_(2i)at the time of state switching of the pressure switch in adepressurization process of the pressure switch, where i=1,2,3 . . . ;an estimated value acquisition step for performing fitting estimationfor the detected upper switching values (including the initial upperswitching value) or the detected lower switching values (including theinitial lower switching value) that were acquired in the last two ormore times, and acquires an estimated upper switching value

or estimated lower switching value

of the pressure switch, where r=1,2,3 . . . ; a judgment step forcomparing the difference between a maximum value and a minimum valuebetween/among the estimated upper switching values or the estimatedlower switching values acquired in the last two or more times with aspecified value δ, and returning to the detected value acquisition stepif the difference is greater than or equal to the specified value δ; ortaking the estimated upper switching value or the estimated lowerswitching value acquired in the last time as an upper switching value orlower switching value of the pressure switch, if the difference issmaller than the specified value δ; wherein, in the detected valueacquisition step, the pressurization rate or depressurization rate isdecreased from a pressurization rate v_(1(i−1)) or depressurization ratev_(2(i−1)) in a last time of state switching of the pressure switch, arate adjustment value is added to the decreased pressurization rate ordepressurization rate, and the resultant pressurization rate ordepressurization rate is used to change the pressure in the pipeline;wherein, in the detected value acquisition step, the rate adjustmentvalue is decreased as the pressure value in the pressure pipeline iscloser to the detected upper switching value (including the initialupper switching value) or the detected lower switching value (includingthe initial lower switching value) that was acquired in the last time;and wherein, the rate adjustment value is a function of the pressurevalue in the pipeline expressed by ΔV_(ij)=k(R_(i-1)−p_(j)), and thepressurization rate is expressed by V_(ij)=θv_(1(i−1))+ΔV_(ij), where,ΔV_(ij) is the rate adjustment value in detection step j in the detectedvalue acquisition step i, V_(ij) is the pressurization rate in thedetected value acquisition step i, v_(1(i−1)) is the pressurization ratewhen the detected upper switching value was acquired in the detectedvalue acquisition step (i−1), R_(i-1) is the detected upper switchingvalue detected in the detected value acquisition step (i−1), p_(j) isthe pressure value in the pressure pipeline detected in the detectionstep j, k is a pressure adjustment factor, θ is a rate adjustmentfactor, and k≥0, 0<θ<1 i=1,2,3, . . . , j=1,2,3 . . . .
 15. The methodfor detecting the switching value of the pressure switch according toclaim 14, wherein, in the estimated value acquisition step, fittingestimation is performed based on the relation between the detected upperswitching value and pressurization rate or between the detected lowerswitching value and depressurization rate with a polynomial fittingmethod based on least square, and a corresponding estimated switchingvalue when the pressurization rate or depressurization rate of zero istaken as an estimated upper switching value or estimated lower switchingvalue.
 16. The method for detecting the switching value of the pressureswitch according to claim 14, wherein, in the detected value acquisitionstep, a detected upper switching value R_(i) or detected lower switchingvalue F_(i) at the time of state switching of the pressure switch isacquired in a way that ensures the pressurization rate ordepressurization rate at the time of state switching of the pressureswitch is different from the pressurization rate v_(1(i−1)) ordepressurization rate v_(2(i−1)) in the last time of state switching ofthe pressure switch.
 17. The method for detecting the switching value ofthe pressure switch according to claim 14, wherein, in the judgmentstep, the specified value δ is a preset accuracy, and its value iswithin a range of 0.2-0.5 times of the accuracy of the pressure switch.18. The method for detecting the switching value of the pressure switchaccording to claim 14, wherein, in the initial value acquisition step,the pressure in the pressure pipeline changes at a high pressurizationrate or depressurization rate, until ON-OFF state switching of thepressure switch is detected; at that point, the pressure value at thetime of state switching of the pressure switch is acquired as an initialupper switching value R_(i) or initial lower switching value F_(i), andthe pressurization rate or depressurization rate at the time of stateswitching of the pressure switch is taken as the initial pressurizationrate v_(1i) or initial depressurization rate v_(2i).
 19. A device fordetecting the switching value of a pressure switch, comprising apressure generator, a pressure sensor, and a pressure pipeline, wherein,the pressure generator and the pressure sensor communicate with thepressure switch through the pressure pipeline, the pressure value in thepressure pipeline is adjusted via the pressure generator, so that thepressure switch is switched between an ON state and an OFF state;wherein, the device further comprises an initial value acquisition unit,a detected value acquisition unit, and a judgment unit, wherein: theinitial value acquisition unit controls the pressure generator to changethe pressure in the pressure pipeline, acquires a pressure value as aninitial upper switching value R₀ and a corresponding pressurization rateas an initial pressurization rate v₁₀ at the time of state switching ofthe pressure switch in a pressurization process of the pressure switch,or acquires a pressure value as an initial lower switching value F₀ anda corresponding depressurization rate as an initial depressurizationrate v₂₀ at the time of state switching of the pressure switch in adepressurization process of the pressure switch; the detected valueacquisition unit controls the pressure generator to change the pressurein the pressure pipeline, acquires a pressure value as a detected upperswitching value R_(i) v_(1(i−1)) and a corresponding pressurization ratev_(1i) v_(2(i−1)) at the time of state switching of the pressure switchin a pressurization process of the pressure switch or acquires apressure value as a detected lower switching value F_(i) R_(i) and acorresponding depressurization rate v_(2i) v_(1i) at the time of stateswitching of the pressure switch in a depressurization process of thepressure switch, in a way that ensures the pressurization rate ordepressurization rate at the time of state switching of the pressureswitch is smaller than the pressurization rate v_(1(i−1)) F_(i) ordepressurization rate v_(2(i−1)) v_(2i) in a last time of stateswitching of the pressure switch, where i=1,2,3 . . . ; the judgmentunit receives the data values acquired by the detected value acquisitionunit, compares the difference between a maximum value and a minimumvalue between/among detected upper switching values (including theinitial upper switching value) or detected lower switching values(including the initial lower switching value) that were acquired in thelast two or more times with a specified value δ, and instructs thedetected value acquisition unit to perform the next time of acquisitionoperation if the difference is greater than or equal to the specifiedvalue δ; or takes the detected upper switching value or detected lowerswitching value that was acquired in the last time as the upperswitching value or lower switching value of the pressure switch, if thedifference is smaller than the specified value δ; wherein, in thedetected value acquisition unit, the pressurization rate ordepressurization rate is decreased from a pressurization rate v_(1(i−1))or depressurization rate v_(2(i−1)) in the last time of state switchingof the pressure switch, a rate adjustment value is added to thedecreased pressurization rate or depressurization rate, and theresultant pressurization rate or depressurization rate is used to changethe pressure in the pipeline; wherein, in the detected value acquisitionunit, the rate adjustment value is decreased as the pressure value inthe pressure pipeline is closer to the detected upper switching value(including the initial upper switching value) or the detected lowerswitching value (including the initial lower switching value) that wasacquired in the last time; and wherein, the rate adjustment value is afunction of the pressure value in the pipeline expressed byΔV_(ij)=k(R_(i-1)−p_(j)), and the pressurization rate is expressed byV_(ij)=θv_(1(i−1))+ΔV_(ij), where, ΔV_(ij) is the rate adjustment valuein detection step j in the detected value acquisition step i, V_(ij) isthe pressurization rate in the detected value acquisition step i,v_(1(i−1)) is the pressurization rate when the detected upper switchingvalue was acquired in the detected value acquisition step (i−1), R_(i-1)is the detected upper switching value detected in the detected valueacquisition step (i−1), p_(j) is the pressure value in the pressurepipeline detected in the detection step j, k is a pressure adjustmentfactor, θ is a rate adjustment factor, and k≥0, 0<θ<1, i=1,2,3, . . . ,j=1,2,3, . . . .
 20. A device for detecting a switching value of apressure switch, comprising a pressure generator, a pressure sensor, anda pressure pipeline, wherein, the pressure generator and the pressuresensor communicate with the pressure switch through the pressurepipeline, the pressure value in the pressure pipeline is adjusted viathe pressure generator, so that the pressure switch is switched betweenan ON state and an OFF state; wherein, the device further comprises aninitial value acquisition unit, a detected value acquisition unit, anestimated value acquiring unit, and a judgment unit, wherein: theinitial value acquisition unit controls the pressure generator to changethe pressure in the pressure pipeline, acquires a pressure value as aninitial upper switching value R₀ and a corresponding pressurization rateas an initial pressurization rate v₁₀ at the time of state switching ofthe pressure switch in a pressurization process of the pressure switch,or acquires a pressure value as an initial lower switching value F₀ anda corresponding depressurization rate as an initial depressurizationrate v₂₀ at the time of state switching of the pressure switch in adepressurization process of the pressure switch; the detected valueacquisition unit controls the pressure generator to change the pressurein the pressure pipeline, acquires a pressure value as a detected upperswitching value R_(i) and a corresponding pressurization rate v_(1i) atthe time of state switching of the pressure switch in a pressurizationprocess of the pressure switch, or acquires a pressure value as adetected lower switching value F_(i) and a correspondingdepressurization rate v_(2i) at the time of state switching of thepressure switch in a depressurization process, where i=1,2,3 . . . ; theestimated value acquiring unit receives the data values acquired by thedetected value acquisition unit, performs fitting estimation for thedetected upper switching values (including the initial upper switchingvalue) or the detected lower switching values (including the initiallower switching value) that were acquired in the last two or more times,and acquires an estimated upper switching value

or estimated lower switching value

of the pressure switch, where r=1,2,3 . . . ; the judgment unit receivesthe data values acquired by the estimated value acquisition unit,compares the difference between a maximum value and a minimum valuebetween/among estimated upper switching values or the estimated lowerswitching values that were acquired in the last two or more times with aspecified value δ, and instructs the detected value acquisition unit toperform the next time of acquisition operation if the difference isgreater than or equal to the specified value δ; or takes the estimatedupper switching value or the estimated lower switching value acquired inthe last time as an upper switching value or lower switching value ofthe pressure switch, if the difference is smaller than the specifiedvalue δ; wherein, in the detected value acquisition unit, thepressurization rate or depressurization rate is decreased from apressurization rate v_(1(i−1)) or depressurization rate v_(2(i−1)) in alast time of state switching of the pressure switch, a rate adjustmentvalue is added to the decreased pressurization rate or depressurizationrate, and the resultant pressurization rate or depressurization rate isused to change the pressure in the pipeline; wherein, in the detectedvalue acquisition unit, the rate adjustment value is decreased as thepressure value in the pressure pipeline is closer to the detected upperswitching value (including the initial upper switching value) or thedetected lower switching value (including the initial lower switchingvalue) that was acquired in the last time; and wherein, the rateadjustment value is a function of the pressure value in the pipelineexpressed by ΔV_(ij)=k(R_(i-1)−p_(j)), and the pressurization rate isexpressed by V_(ij)=θv_(1(i−1))+ΔV_(ij), where, ΔV_(ij) is the rateadjustment value in detection step j in the detected value acquisitionstep i, V_(ij) is the pressurization rate in the detected valueacquisition step i, v_(1(i−1)) is the pressurization rate when thedetected upper switching value was acquired in the detected valueacquisition step (i−1), R_(i-1) is the detected upper switching valuedetected in the detected value acquisition step (i−1), p_(j) is thepressure value in the pressure pipeline detected in the detection stepj, k is a pressure adjustment factor, θ is a rate adjustment factor, andk≥0, 0<θ<1, i=1,2,3, . . . , j=1,2,3, . . . .